However, there is no need to have miners switch work once per share. Bitcoin's blocks and transactions need to be serialized in a canonical ordering in order to prevent double-spending or transaction conflicts, but with p2pool there's no equivalent need for each share to come one after another. All that a share needs to do is prove that work was done in a way that benefits other p2pool users, which means (a) accurately pays out to other p2pool users and (b) is working on the correct block height at any given time.
How do you implement PPLNS without consensus on the order of shares?
I think when you make this kind of change to allow sibling shares you will need to introduce more complex incentive models to try to make the payouts "fair" and unexploitable (including hop-proof), not unlike how GHOST or ETH's version of it attempt to do so with block rewards. That sounds like a mess.
In any case I'm glad to hear that firmware issues seem to be resolved on the latest Antminers, potentially reducing the need for this.
