Looks like an interesting proposal, but it doesn't seem to quite match the goals you mentioned. As you do mention, this mining pool coordination doesn't get rid of the need for mining pools in the first place. So it doesn't satisfy item 1 on your goal list afaict.
The primary benefits over what we have today that I can see are:
1. increased payout regularity, which lowers the viable size of mining pools, and
2. Lower on chain footprint through combining pay outs from multiple pools.
Am I missing some?
These are interesting benefits, but it would be nice if your post was clearer on that, since the goals list is not the same as the list of potential benefits of this kind of design.
As far as enabling solo mining, what if this concept were used off chain? Have a public network of solo miners who publish "weak blocks" to that network, and the next 100 (or 1000 etc) nice miners pay you out as long as you're also being nice by following the protocol? All the nice optimizations you mentioned about eg combined taproot payouts would apply i think. The only goals this wouldn't satisfy are 3 and 5 since an extra network is needed, but to be fair, your proposal requires pools which all need their own extra network anyways.
The missing piece here would be an ordering of weak blocks to make the window possible. Or at least a way to determine what blocks should definitely be part of a particular block's pay out. I could see this being done by a separate ephemeral blockchain (which starts fresh after each Bitcoin block) that keeps track of which weak blocks have been submitted, potentially using the pow already in each block to secure it. Granted that piece is a bit half baked, but it seems quite solvable. Wdyt?
One thing that jumped out at me as not safe is throwing block rewards into a channel and being able to spend them immediately. There's a reason block rewards aren't spendable for a while, and channels don't solve that problem, do they? Why not simply reduce the on chain wait time for spending block rewards at that point? Seems like the consequences would be the same.