This is purely semantics, but maybe refer to the section as “Critique” rather than editing? Only speaking for myself, that makes me think of input on the writing and structure, rather than just grammar, and people might be more open to taking part if they feel they’ll get high-level feedback.
If we say it’s for editing and spellchecks, some people might be too proud to take part, you know?
(I’ll be frank — my own impatience might hold me back from posting stories to it, but I’d be happy to take part on some level since I love playing with words. Like AB, I do it professionally, though, so it wouldn’t be an everyday thing for sure… not that the call for it would be THAT great.)
So, to sum up — I think it’s a great idea; we just need to get people to buy in. It’s clear these forums aren’t highly trafficked, so publicizing it would be job one.