I know the flood won't be in this game but if there was a multi-player flood race then:
"Town Centre" = outbreak marker upgrades to Premature Grave Mind upgrades to mature gravemind (all of these should look like a forerunner spire but should also look meatier as the grave mind ages.
"barracks" = Floodified UNSC or Covenant buildings or Floodified Map Structures (Soecifically for floodthings)
"turrent" = Flood spore tower thingy.Flood spike spitter
"air unit building"= Floodified drop pad
"constant gravemind area upgrade"= Infection form creater
"gravemind (mature) + barracks + "calcium resource"" = pure form flood
"barraks and calcium"= Combat forms, bloated ones, infection form packs (10-20 infection forms)
We all should know what forms of flood thier are so my last thought is an upgrade of the outbreakmarker/gravemind.
The upgrade dictates what architecture you get and what upgrades you get. UNSC/Covenant choices.
The upgrade sounds similar to the Company of Heroes, Airborne| |Infantry| |Mechanized(?) but with differnt builds for our 2 choices.
NOTE: grave-mind grows around the outbreak marker so that building will be the same whatever the choice you make.
And the concept picture thing looks great. (UNSC BASE!)
Halo Wars will never beat ANIME