ok, i've been thinking and:
mongoose: no guy, AR guy, Rocket Guy
warthog: front bumper (better ram), LAAG, gauss, rocket, rocket passenger
falcon: front turret, side MGs, side grende launchers, transport less troops than pelican
covenant leader powers are changed to be like UNSC powers: spirit transport, glassing airstrike etc.
play as the neutrals
new neutral: promethian - knights, crawlers, watchers
change the UNSC anti infantry from flamers to snipers
swap cyclops for mantis
add in mammoth that does the same as the elephant but spawns warthogs/mantis' instead
more of the single building pads
add upgrade buildings: infantry- training centre, vehicles (air and land) -garage or repair shop
whadaya think, eh?