We never discussed Mechanized Infantry vehicles in the prep to this. You didn't tell me you were intending on using a desert terrain. If you had, I would have strongly urged Mech and armor. Light infantry, which is what we are now, are best deployed in wooded terrain, Mountainous terrain and Built up city areas (MOUT - Military Operations in Urban Terrain). The original iteration of this RP was set in a Serengeti; clear open grassy plains with copses of trees dotting the landscape. That terrain is best for Mech and Armor, just like a desert, but this is also good for a Light/Heavy mix. You can deploy light infantry in the wooded and built up terrain with armor and mech in the open country.