Straight prop.
I'd be willing to donate premium percentage, so say like 2.5% to 5% to have hopping access along with a reliable API.  Tie the pool stats into a the user API, which can only be enabled after you donate a predetermined percentage.  You can then redistribute this fund to your full time miners as "additional hopper income".  I think the ~50GH/s will definitely help a pool out and also attract more miners.  Even if most hoppers leave after 43% of shares being submitted, there is still an incentive for finishing a block, because without the block being finished no one will get payed hopper or not.
http://www.digbtc.net/ DigBitcoin resurrected itself after switching back to purely prop after trying LNSMPPS.