Seriously, there are a couple of them from weegee:
http://forums.datarealms.com/viewtopic.php?f=24&t=15816 - Attack coalition and then defend the outpost from coalition.
http://forums.datarealms.com/viewtopic.php?f=24&t=15612 - Defend Base from dummies
http://forums.datarealms.com/viewtopic.php?f=24&t=16201 - Defend 2 Ronin from Coalition, sniping them

1. Open skirmish
2. Select desired map
3. Select 'Death'
4. Build big bunker with guys and ♥♥♥♥
5. Add brain unit in some room with a door
6. Start game
7. ???
8. Every defense mission ever.

*aims at Warguy*

"Falcon Punch!"

*Warguy dies*

On topic:

Astro is very fun and has replayability factor.

viewtopic.php?f=24&t=15247

And hey, if you liked maginot, you can always make a duplicate and then increase its difficulty.
I've found that a maginot with a wrapped level is actually pretty good for skirmishing in, though because I dislike long games its a little impractical to defend.