The Regiment part was largely due to limited dropship avaiablility for the drop on Circinus and for the moment it stuck.Oh we are doing divisions? We generally seem to deploy by regiment so figured that was what ussually use on offensive or at least what can be transported but sure divisions are awesome.
Now, there is nothing keeping us from going to deploy full divisions. Once the ligistics and other issues are sorted out. Maybe some sort of version of the Planetary Settlement Kit for local resupply with non-food items to shorten the logistics chain.