Sorry, but maybe I wasn’t clear. I’m not suggesting that anyone expect “the payoff of seeing a new feature”. The only payoff is mitigating threads like this one. So you don’t need a “champion”.
Instead of a PEP, it could simply be a wiki of commonly proposed ideas. That keeps the editing barrier small. Each idea would have its own page, which could look something like:
Main idea: Multi-line anonymous functions
Proposal details: … [variations of syntaxes, e.g.]
Links to discussion threads: …
Main arguments against: …
Main arguments for: …
Related PEPs: …
This doesn’t need much effort. You could probably lift most of these sections from this thread verbatim.