Red vs nigeria/chad/france, 6625 vs 55000 pts (although it didn't seem to make much difference). 200 missions, 200x160 desert maps. Jan-Feb 2013.
Initially bought only 13 point FN FAL insurgents, plus BMPs for river crossings. -20% repair. Autodeploy & AI control all missions. HQ converted to SA 10 and retreated off map in deploy. Had to restart the game in one mission where I failed to do this.
Various core troop upgrades experimented with. Eventually cheated, settled on Mi 24 core and Leclerc crossbought auxiliaries by mission 130 or so.
During some river crossings I just bought a bunch of helis and artillery and got a draw.
Observations:
Initially the Chadians turned out to be hardest because of their numerous APCs. The AI doesn't spread the RPGs out evenly so when insurgents run into armor they have difficulty. The French were easiest because of their high unit cost.
Once I started upgrading to real units (tanks, helicopters etc) the French became harder because of their ridiculously deadly Leclercs.
Buying better units makes the game a lot harder. A cheap insurgent force almost always wins because the enemy buy points equal yours. But because the Para Engineers aren't as cost effective as the insurgents I started to lose as I upgraded my troops.
Don't be in a rush to kill tanks. With cheap infantry, whatever losses you sustain to them add to the tank's experience, so you get most of those lost points back when you kill the crew.
Sell off your damaged or obsolete units after a battle. It's cheaper than changing them.
ATGMs are far more effective at shooting down helicopters than SAMs.
During assault missions a lot of my helicopters are destroyed or immobilized flying over mines, which is strange.
Swarming the enemy with BTR 40s until they run out of ammo is almost but not quite viable strategy. It would be a viable strategy if there was no formation limit though.
Never buy more than 55000 pts worth of core troops or you'll break the game.
Tanks are easier to kill with 99% hit chance Kokons when dug-in because the front hull is never hit while the side turret is.
If there was a mineclearing version of the Leclerc it would be the perfect tank.
Other fun ways to break the game:
Buy nothing but insurgents.
Buy nothing but cluster artillery.
Buy nothing but M1A1HA Abrams for desert maps.
Buy nothing but helos and a few airmobiles to take objectives.
Create a custom scenario where you are Iraq using captured M1s and the AI is America using captured T-72s.
Convert your HQ to an SA 10 and then complain about it to Don when the icon doesn't show up.
Conclusion:
I was unable to truly break the game. None of my buy choices could assure me a consistent minor victory. The Red OOB seems to be balanced against its opponents such that any combination of buys will do no better or no worse, within reason.