A few things I'd like to see in the next version, allowable in MA terrains:
A forward airbase: No bomber hangars, no ord bunkers, no troop barracks and no vehicle hangar. Just a couple of fighter hangars, a short runway, a reload pad, some AA, fuel bunkers and a tower. It should have a lot of temporary looking buildings (tents etc.) and maybe a pierced steel, dirt or grass strip and its own "F" designation on the clipboard map. The idea is for MA terrain builders to be able to put a defensive fighter airbase somewhere, i.e. tank town, without bringing in a bunch of bombers and jabos as well. Also, apart from the base guns the only defence against GV attack would be the three AT cannon armed aircraft, so these might get some more use.
AA or AT bunkers: There could be a heavy AT gun in a concrete pillbox, and also a variety of concrete flak towers or bunkers with one or more light or heavy AA guns etc. The terrain's creator would be able to be place these like a shore battery near to a base. There would need to be some restrictions on how many and where they could be placed. Perhaps not on the same tile as the base or town, but on flat terrain and within a certain distance. Shore battery placement currently has similar rules IIRC. In-game these emplacements would show up in the guns selection screen in the same way as the shore batteries do now. Being protected by concrete they would need bombs, rockets or shells to take down. This would add a degree of variety to each field's defences and would add some interest for the terrain creator, siting AT bunkers in sneaky spots between the SP and the town etc would be fun.
Eye candy objects: A selection of stuff that can be placed into an MA terrain that has no effect on gameplay other than for visual interest and maybe cover. These could include ruined factories, groups of ruined houses, a partially sunken shipwreck, crashed and burnt out aircraft and so on. Making them already destroyed prevents anyone trying to waste ordnance on them. It also adds some sign that there is a war going on. A terrain builder could dot these about to add visual interest and also to create mini environments for GVs to fight in and around. There could be restrictions on how many can be placed near a field to prevent FPS issues.