The easiest way is a two step approach:
- Release your plug-in to the public. Once it’s live, you’ll start getting feedback from end users in addition to developers. If you want, release it as a “beta” version and heavily emphasize that in the readme file.
- Ask. There are veteran WordPress developers everywhere: here, on the WP-Hackers list, at WordPress jobs, stalking @wordpress on Twitter, etc. It’s just a matter of throwing your plug-in out there and asking for feedback.
In general, follow the same steps as you would getting a Core patch looked at by a developer:
- Write it
- Document it
- Contact a developer (either broadly through one of the above channels or directly if you can) and ask for feedback
As far as transforming the kind of “mentorship” that occurs on this site into something more concrete, that would be an organic process. As you’ve already mentioned, efforts to create a kind of plug-in review process before actually reviewing anything seem to have stalled. The only way to get anything off the ground is to actually start doing it. So don’t just talk about finding a veteran developer and getting feedback, go out, find one, get your feedback, and write down how the process went.
Then it can be repeated with future plug-ins and future developers. But you’ve got to start somewhere …