Intresting thoughts...
I've been thinking about something similar, and what could be done in an Mod with the current system (face it, Conquests is finished, and the next expansion is far away...).
How about this: three new strategic resources, called "Desert training evnironment", "Arctic training evnironment" and "Tropical training evnironment".
Certain units would have upgrades (or alternative units) at the same tech level as the unit itself becomes available. These upgrades is exactly the same unit, only with the appropriate strategic resource.
Confused? Some examples of how it might work:
Desert now costs 2 movement points.
The tech Horseback Riding now enables 2 units: the ordinary horseman (req: Horses) and the Beduin horseman (req: Horses & Desert training conditions).
They have exactly the same cost stats (30shields, 2-1-2), but the Beduin horseman
ignores the extra movement cost for deserts., just like the Keshik ignores mountains. So a Civ with experience in Desert fighting will most likely outmanouver their opponents.
Desert and Tundra now costs 2 movement points.
The techs Computers and Synthetic Fibers enables Mech Inf and Modern Armour as before - but now they also allow Arctic and Desert versions, requiering Arctic and Desert training conditions respectively, who ignore the move cost 2 of Tundra and Forest (Arctic version) and Desert (Desert version), respectively.
Replaceable parts allow Guerilla as before, but with "Tropical training conditions" you can build a Guerilla with (I'm undecided here) move 2 and ignore Jungle & forest terrain penalties or it could treat all terrain as roads like the conquistador.
All these units could be represented by the different animations in the C&C forum.
And the cool thing about the different "Training conditions" being strategic resources, is that you can "buy" them - think of it as joint excercises, etc. Teach youur allies how to fight on your home ground, in case you ever need them in the future - and hope that they won't betray you and use the training against you...
