I think this is a great idea.

My only concern is, what if some well-meaning person puts in a poorly constructed claim, and then that creates a counterproductive precedent.

I think ideally, someone like Software Freedom Conservancy or the Linux Foundation or the FSF or whoever would take charge of doing it, taking advice from patent attorneys in the process.

Maybe there is some UK patent attorney reading this who is willing to take it on pro bono?

A bit pedantic (since my wife is in IP), but you don't need a patent attorney for most patent things, you just need a patent agent. (Who may also be an attorney.) Non-attorney patent agents can handle basically everything related to patents other than litigation.