Just thought of something... to fix the whole silly 'tundra colonisation' problem... is it really realistic to have engineers planting forests in tundra? I don't think so, honestly... how about removing the ability of workers to plant forests in tundra... then given that tundra is not habitable in DyP, it would mean that tundra would remain so - with the exception of the few bits that might bear some forest. This would mean you could turn most of Greenland on the DyP Earth map into flat tundra, and not worry about the AI colonising it stupidly (not that it has in my games so far...).
You could also put more resources in those areas then, which would mean that a ****ty little town growing from only one square of forest and some sea would be very worthwhile as it would be the only way to access all those resources...
Just a thought
Oh, and I agree on the marines->grunt upgrade path comment... marines should go straight to spec ops - actually they should not even upgrade to spec ops, but simply coexist as a cheaper alternative.
Also, why the urge to include theocracy? I would say, dump theocracy as it is a fairly useless, self-destructive government (like in the real world...). The AI has troubles enough as it is... providing it with the option to hurt itself by switching to theocracy is not useful. Also think realism - why would a democractic nation turn to theocracy in times of war? It's not realistic at all. Imagine the US getting attacked by canada and turning into a theocracy to defend itself better???? Surely not

Democratic governments that respect civil rights have consistently outproduced and out-warred despotic governments. There is simply no reason for the inclusion of theocracy in the mod - unless you go for the CtP option of giving it a hugely cheap 'fanatical terrorist' unit that can suicide-bomb cities and units (and do them a lot of damage), and a more expensive suitcase nuke terrorist that can be built without access to uranium.
Otherwise I see no point to theocracy in this game.
Other comments I can think of, for govts:
Fascism is a hugely corrupt government. It should be as bad as chiefdom, but have a high draft limit and very large military police limit (say 5). Also if you really want to include it you should also have a cheap but effective fascist unit like in CtP to counterbalance a much higher self-destructive rate (which it should have). I can't really understand why fascism should be included, as to be honest (and historically accurate) it is more akin to thug-led anarchy than to an actual modern form of government, and is probably more than adequately represented by despotism or even chiefdom.
Sorry for the long post... just had a lot of ideas together that needed expressing

Hope they help someway.
Daniel