I remain unconvinced that segwit payment channels are necessary for an incremental improvement. You're welcome to believe in the God of Gaps, but code is written by people and unless you lock them in a hotel room and pay both the cleaning and writing bills (not to mention plumbing, electricity, faraday cage maintenance, etc), people write code slowly and generally pick the lowest-hanging fruit off the least-forbidding tree.
See the quote by this guy:
There are qualified developers who I have spoken with that are willing to work on P2Pool, and Forrest is still around, if there was a viable proposed solution I would certainly contribute.
The real problem is solving P2Pool's scaleability challenges, and they are hard problems to solve that require inventing a solution.
Right now anyone who wants to work on the idea in OP should just work on Lightning. The payment channels can be connected to Lightning so then hashers would be paid to their LN wallet with the funds available for spending immediately.
Why not just mine to a multisig of the smallest N miners, and leave them to coordinate between them how the payouts are distributed? This can start out as manual config mediated by a trusted Mth party, and evolve into all your payment channel voodoo wowee.
Maybe, I'd recommend fleshing this idea out more so it's easier to follow.