T78: Hmm. I like this idea, reminds me of how I used to use GDI rifle squads. That said there's already a "good ground" mechanic that offers the toughness bonus you speak of, but they're locked to the positions they're placed in the mapmaker. I do think that a suppression system would be nice for infantry, in the vein as that offered by Command and Conquer games, but it'd probably take a surprisingly large amount of effort to make infantry hit the deck when under heavy fire to get a cover bonus (this would entail a set of animations for this action, for a start, which may have to be built from scratch, to say nothing of coding) so as much as it would be awesome I doubt it's planned. Possibly a less manpower-intensive variant would be doable; just give them the cover bonus and movement speed debuff usually applied to suppressed infantry to them without animations, and maybe a glow to indicate the effect, but that's cheap and nasty, which are two things that do not fly around here.
Counter-suggestion: have them be able to place a bunker on the map. A literal bunker; like the ones you can build. They do count as placable; the fun part would be convincing the engine to let you place them in singleplayer without a buildpad. That said, the assets are already in engine, and we can get some mileage out of the faction-specific bunker models. It would be bloody overpowered if the bunker nerfs weren't rolling out soon, but with them... Maybe? I mean, it would add flavour and actual utility to these units we generally throw at reinforcement points and buildpads without ever ordering into direct conflict.
On the topic of capturable structures, can we get a "control module" build order on capturables, perchance? To lock the capturable to the taking side without needing an infantryman standing on it. Just an idea; tieing up an infantry squad (often the last one in his company, so he keeps taking up the pop point) to hold something I might need later is good strategy but bad math when we have ten pop points to work with. Just an idea,