Have you given any thought to having multi-algorithm rigs?  I'd have to check if cgminer and vertminer will coexist on the same box if one of them is idle at any given time, but if so, it'd be handy to point cgminer at betarigs port X and vertminer at port Y, and then have the same rig be rentable for both.

If someone rents it for Vertcoin, it becomes unavailable for scrypt, port Y starts serving up shares, and vertminer goes to town.  And likewise for scrypt.