I like "max. 1 battery per maneuver company" and "max. 10% for arty"...
Artillery is a big area where ground rules come into play. There is usually some percentage limit in games I play of roughly 10-15%. I've never had a battery limit per company, but 10% does usually limit the number anyhow. That's also a good one.
On arty tend to play the following
Meeting engagements only
No pre bombardement except smoke & SEAD aircraft as the SEAD should have done there job.
For all other engagements happy to let fly as see fit the attacker is normally player one so is softening up if desires.
10% is often quoted by people sometimes 15% if so I take to include all arty including stuff that comes with companies, some people include air in this most dont.
Sometimes say no ammo dumps for meetings as not set up & some people say no CM reloads.
Other things people suggest
Max 1 snipper per inf co
Max 1 size 0 unit per platoon as in AT teams etc.
This is only if company does not come with them.
Only real proviso I have is if helos possible map should be 120 wide minimum as they are fast need space to operate.
I think these are the major things as mass arty makes for a slow game as does lots of size 0 units.
If people set air rather than using XXX feature a bit of common sense, certain theatres say Viietnam you might get a lot of air but 4 airstrikes (8 planes) is a lot to support 2 or 3 companies in my opinion in a meeting.
Just thought airdrops (not air) must be in first half of game & must come from your end of the map, start from your 3 arrows. This is because if no one fires at despite seeing replay may not show them at all so no idea of flight path. Used to be a bigger problem I think for player 2 though not sure if still applies