pPlot:SetImprovementType(GameInfotypes.IMPROVEMENT_ALIEN_NEST)
if (pPlot:GetResourceType(-1) == GameInfoTypes.RESOURCE_XENOMASS) then
...
end
But then they could capture cities so you would have to run some Lua at the end of their turn and raze cities they might own, but there was no easy way to run Lua at the beginning/end of arbitrary AIs turns without some events that were added to modified dlls.This was covered a little in my thread about improvements ("Creating a new Improvement, has anyone done it?"), I pointed out that it may be possible to drop a new civ down (on the specific location) and that civ would have the same stats / appearance of aliens and could be hostile towards players and AI but friendly towards the alien faction. This is the only work around that I could see working, however would required major modding.