1. I agree with Destructavator.
2. There is one thing in your proposal that startled my mind:
... Thus forcing the player to keep a well armed garrison in his bases at all times.
What if the campaign would support 'alien double strikes' as a new tactical variant (at >= hard level) ?
ie. They lure your dropship (and your soldiers) away from your base with a terror mission, then (with the right timing, so your dropship can't be back in time) attack that base with a second ship
That would feel like a kick in the groin for the unaware player *bg*.
I don't know that part of the code at all, but I figure it *might* be doable with medium effort.
@geever:
Would you mind to look at that code a bit and check if such 'multiple coordinated alien attacks' would require a complete redesign or just a few keystrokes ?