You misunderstood on one aspect. When I said 240+ that was a combination of tanks, armored cars and half-tracks and not just 240+ half-tracks. The mission was a delay. It was a high visibility desert battle. Unfortunately, the conditions generated dust. I really could only see lead units and a massive cloud of dust behind them. This allowed them to get closer than I would have liked. I destroyed units I could see up front, but in the cloud of dust, there were lots of other units. To make things worse the AI forces, British in this case, were using half-tracks. It was bad for two reason. The first is they were able to keep up with the advancing tanks. Usually, tanks will out run advancing trucks allowing me to dispatch the force is phases. There are riders on the tanks, but the AI almost always seems to do that. The other problem was half-tracks are armored, meaning I had to use AP rounds to destroy them. Terrain was such that there was a lot of rough ground and soft sand, making lateral shifting of me units a timely process. Infantry at this point, mid 1942 I believe, didn't have much in the way of infantry AT weapons. All the heavy work had to be done by 17 PzKw IVf2 tanks, 6 StuG IIIf assault guns, 6 50mm ATGs and 6 75mm ATGs. The ammo situation got so bad I was engaging targets with direct fire from my 6 SPAs and 6 recon tracks mounting 37mm guns. At the end of the battle, my center and right flank elements only had HE left with the exception of one 75mm ATG. I was starting to pull tanks off the line to head for resupply in the center and right, hoping my infantry would by me time. Units on the now quiet left flank were shifting, but I figured it would take 5 turns for them to get there. Then, for some reason, the AI just quit. I did an AAR on the this battle.
http://forum.shrapnelgames.com/showthread.php?t=41277
The thing about the number of units you can have, the limit a player can pick is 300. An additional 200 are slotted for support use in situations such as beach landings to account for landing craft that are automatically added. All told, you can have 500 maximum. Since the AI force is completely under its control, it can go up to 500 units.
The 23 tank killing guns would be my AFVs. There are 17 Panthers and 6 Tigers. I've actually got 7 tracks with 37mm guns also and one with a 75mm howitzer, but those aren't intended to slug it out with tanks. The can handle the odd armored car just fine however. I use to have ATGs, tank destroyers and assault guns, but got rid of them. My 6 StuGs were upgraded to Tiger Is, while my 6 75mm ATGs went to Elefants and then they were deleted. With their experience, the Elefants were over 200pts each. In a defend mission, the AI attacks with a 5:2 ratio of points, so my Elefants and their six 88mm guns gave the AI an additional 3,000 points to use to purchase units. Six guns just weren't worth it. If I had to destroy KV-1s maybe, but they weren't needed to kill Shermans.
The funny thing about that last defend battle where all my tracks were on the back row, visibility was 20. I didn't expect the AI to have aircraft. My rational was if they didn't have aircraft, artillery would be very heavy and I wanted to keep the tracks away from it. Artillery usually doesn't hit the back row. It was heavy, but a dozen aircraft made it rougher. Smoke from burning trees, vehicles and artillery strikes made visibility very difficult. I had to hit the "clear" button just to find my own units in that mess, but the aircraft still found targets. Only once did it attack one of their own. What you suggested about keeping them about 10-20 hexes behind the AFVs wouldn't have been practical in this case. That would have put them behind some very large hills and in the middle of the woods. There are instances where the suggestion would have merit, however. This position wasn't ideal for defending, but it was what I had to do and I've seen worse.
One thing I was wrong about in my core is I have eight SPAA units, four sections and not two. When my force is on the move, one section goes with each SS infantry company and the remaining two sections stay with the armor. In that battle, defend I mentioned above, two sections were deployed on each flank and roughly 15 hexes behind the main line. Their purpose was to intercept any fast moving enemy units that got through on the flanks as aircraft weren't expected. I would have had them more centered if I had anticipated aircraft.
My scouts ride, but I have dedicated transport for that purpose. I have 6 scouts and 6 recon tracks. The recon tracks run the forward, unload them and stay close for support. I usually delay any advances I make about three or four turns to allow the scouts to get out and check the route out before the rest of the core gets there. They typically have spotted the AI line before the column gets there. Spotter aircraft help in this aspect, if they are available. Scouts on the ground are better, but take more time and there are places they can't get to as easily. Sometimes I use them as fighting scouts. They have panzerfausts now and are deadly to AI tanks who move in confined terrain without infantry support. The best option is using both ground scouts and a spotter plane. From a realism perspective, I only take one spotter plane if I can get one at all. One other thing I've done with scouts is air dropped them behind enemy lines. The transport pops in from the back edge quickly and drops them before AI AAA units can respond. Once the scouts are out, I don't really care what happens to the transport since I won't see it again. I do try to keep if from getting shot down, but I don't have any heartburn if it happens. It's a very handy tactic on assault missions, if air transports are available.
I might revisit the tank rider idea. It just seemed to me that a squad draped all over the top of a tank should take heavy casualties if someone opens up with a machine gun. That never seemed to happen. I do prefer having my infantry in tracks, however. That allows them to perform their tasks without altering the task of the tanks. It's not much, but my transport tracks average one kill each, but this doesn't account for the suppression they put on AI infantry before their squad dismounts and really lays into them. The game only counts kills and not assists
The ATGs are purchased out of support points for delays missions. I use to have them in my core, but early war German battles tended to be more offensive in nature. Early on, if I had a mission they weren't good for, I deployed them in an overwatch position. If the AI launched a spoiling attack, they could stop it. Unfortunately, AI artillery would start clobbering them if it didn't have anything better to hit. Then I started bringing them with my core as it advanced. The guns would be deployed to cover objectives captured. This ended up not being that useful because there rarely were any AI units in the area to defend against. That's when I upgraded to the Elefants and I already explained what I did with those. I wasn't happy with Marders either because of their ammo payload. With the tanks I had, I eventually decided I just didn't need them except for in special situations. My core doesn't have anything that isn't useful most of the time. It doesn't have to kill, it just has to be useful. When I do have a delay, I go with the 50mm ATG. It's a small and relatively inexpensive gun. It can't kill heavy tanks, but I have Tigers and Panthers for that role. The 50mm will easily handle half-tracks, armored cars and light and medium tanks. Being that they are small, the target can get into effective range without spotting the gun. It's really a nice little gun.
I don't think I've used Brandenburgers in WinSPWW2, but I used the equivalent in SPWaW. They were real handy in the infiltration mode to put eyes behind the enemy lines. I used them in a PBEM game in SPWaW and managed to get a few SPAs that way. In WinSPWW2, I really haven't looked at them closely, so I don't have a useful opinion.
One thing you mentioned has me thinking now. I haven't restarted my campaign, but I'm running both the patched (3.5) and unpatched (3.0) versions of the game right now. That's because I have a PBEM game in progress with the unpatched version. Until that game is complete, I need to keep the unpatched version running.
You did mention earlier you are playing on a 200x140 map. One thing to think about here is on defend missions, the AI isn't as effective if it can't cover it's whole front. I ran a series of tests on 100x100 maps, which are what I use, where I had the AI assault the AI. It was the tested on the same map each time, with the assaulting and defending nation being 6/44 Germany. The assault to defend ration was 5:2 in both cases. Basically, I ran two models. The light model was defender 2,000 points and the assault force 5,000 points. Here the defender lost 67% of the time. In the heavy model, the defending force has 6,000 points and the assault force 15,000. In this case, the defending force won 80% of the time. Near as I can figure, if the defending AI can't get it's border to border minefield built, it doesn't stand much of a chance, even against itself. The point is, on the large map your intent may be to make things more challenging for you, but it would seem to handicap the AI in defend mission. It's only a possibility that it could handicap it. The assaulting AI finds mine fields by running over them with their tanks, over and over and over again! Leaving 20% of the assault force burning on the mines could also explain why the assault force lost. A person obviously wouldn't do that. As for all the others, I don't know. This was done to try to find the perfect balance between assaulting and defending forces. I just thought I would mention that for consideration.
On a similar note, I did try defending against at AI assault at 6:1 odds (defending 4,000 points, assaulting 24,000 points). That was a challenge. My defending force was almost completely wiped out, but I pulled a draw out of it. I inflicted enough casualties on the AI I got the draw even though I lost all the flags. There were a few things I could have done differently that might have even allowed me to win. If you want a challenge, you should try that.