Valkrionn
The Hamster King
Everything.
Literally, all units. Make the requirement only be Civilization == Doviello. Available to all unitcombats.
I'll put it in that way. If it needs to be toned down, then that can be done rather easily.
Edit: Actually, blocking Workers, Siege, and Naval. All others still have access... So basically, I removed the nonsense classes.
Scavenger sound VERY powerful to me, even at only 5 turns duration.
Personally I would like it just fine if it was just...
Scavenger:
Promotion expires in 5 turns.
Unit costs no maintenance.
Does not cause War Weariness.
Does not cost military support.
Can sacrifice to provide 10 to a city.
Heals an extra 5%/5%/5% in Friendly/Neutral/Enemy territory.
Probably more balanced than what I have.
I'll drop it down to what you suggested for now, though it'll probably be played with a bit later... This promotion is probably going to be one of the most major editions, gameplay-wise.

, so I should be able to get into the program. Assuming I do, in about 2 or 3 months I'll actually be back in college... So it depends on what kind of workload I have.