An idea that may make things even more interesting.

[SpartanCommander]

Thought since your an organization that is being funded by the UN an since some countries don't like each other why not have the game have the player have to play out a political bit a bit and even have different senario's dealing with the military of different Governments.

Like one where you troops arrive at an attack to aid in the local troops fighting off the Aliens.  (So far the only guy's there are unarmed civilians I mean chances are their will be an occasional armed one or police or military).

Another could have where that you have an occasional situation where the normal military manages to intercept a ship as well.  Or even occasionally have where a Govenment's military tries to claim a crashed ship that you arrived at to late to claim.

You could also have a enemy human organization which is trying to use the tech from downed alien ship's for unknown purposes and they are not influenced by the aliens but it would show an interesting antagonist group that you may also have to deal with more than the Aliens and the human group could attack the bases with troops more often than the aliens and sometimes bypassing your defenses.  Thus forcing the player to keep a well armed garrison in his bases at all times.

This would not only prove a challenge but the resources you can recover from the attackers from these assaults could also aid the player greatly.

[Destructavator]

Looking at your points I don't think they would mix very well with the main campaign plot, but IMO they might work for an alternate campaign or mod.

[Duke]

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 ?