No loss impossible unit combos.

[Infiltrator]

I am currently in the early stages of a warrior no-loss challenge (not going for fast completion or anything like that, just no-loss), almost cleared Bolo and about 1/4th through the medals.

I was thinking about getting BK/Bone Dragons, but they alone give me kind of the impression that I'm cheesing the game.

What do you guys suggest for a legitimate 5 slot army? Are the other undead even worth mentioning here? Or would I really need a self-ressurecting remainder of the army, like Paladins, Droids or the like?

I was trying to think of a way to incorporate black dragons, but I've got no idea how they'd go through the boss fights.