Alright. We have a working demo. 
It's still a little rough around the edges so I hope you'll forgive me if I don't provide a link until tomorrow (later today), but it's bedtime and I'm happy with where the code is.
As for the permalinks, well I doubt I can get those to work within the week. The main problem is that the forum plays fast and loose with the url provided. This is good as it probably increases reliability, but leads to situations like this (check out the url and the breadcrumbs). Another issue is that forum and topic slugs are used as handles internally, so the current slug structure is hard-coded into the forum.
Also there is a conceptual problem: given '/forums/alpha/bravo/' is 'bravo' a topic or subforum? What if it's both? We could handle collisions as they occur with preferences, but that leads to unpredictable behavior. Or we could enforce unique slugs globally, but that could break existing permalinks and be a potential security issue.
But what we have now works and is usable, so these url issues are a minor issue.
Anyway, thanks a lot for your support! It's people like you guys and projects like this that makes working on open source projects so much fun.