My .2c would be that if you MUST have a jet of some sort for the map, make it an AA jet (eg: Buzzard with AA loadout) as a complementary element to any ground team that would be carrying launchers for air threats.
As for CAS, as SNAFU points out I don't think Tanoa needs it if the mission framework is going to be built around infantry combat - BUT- if there is logistical reason to implement CAS on Tanoa then I nominate the Pawnee/Littlebird (flares: optional). I think with maybe a bit of loadout tweaking a Pawnee would be just the right risk/reward level for ground combat without it unbalancing the infantry.