Thanks for the feedback guys, it sounds to me like there are no major issues with my concept and there may be some support for the service, so I'll continue with this.
P2Pool is modified to log all submitted shares with diff >= 25 (this is already completed - my patch provides a command line option to specify a logging function. I plan on submitting this to forrestv for inclusion upstream)
I have now done a push request to forrestv's GitHub repo for p2pool for the logging function:
https://github.com/forrestv/p2pool/pull/127The patch calls the logging function for all shares that are submitted by clients, it's up to the called function to perform any filtering needed, such as submitted_diff >= 25.