There are many models.

yvg1900's fee-based software works on a lot of different pools.  It's closed source, but fairly open-ecosystem.

NaN's is similar, though it doesn't support quite as many protocols.

I tried a 10% dev fee on Riecoin decreasing every other day until 2%, and then open sourced it, and that worked out decently (but I wasn't trying to make a living off of this).

The prime stuff is currently a mess, but that's just a matter of time.  Once some of the miners reach performance parity and platform parity, the thing left to compete on is price and pool support.  At some point, the profit margin will get low enough that someone might take the nuclear option and open source their miner.