I'm not sure how much benefits a subforum would bring to us. A discussion thread and a well maintained concluded buglist in the first post (maybe second and third as well) should do the thing. The only big advantage i see is that we could link from the buglist to a thread which explains the bug more detailed but this should work in other ways likewise.
Working in a software company too i also prefer categories for bugs. I would combine your severity 1 and 2 to just 'major bugs'. I don't think that there are that much Severity 1 in future and johan acts very fast in such a case. Using 'major bugs' everyone knows on first look what it meant.
Severity 3 would be just 'bugs' ('minor bugs'? Sounds like peanuts
)
Severity 4 would be 'description bugs'. Maybe including typos but its also possible to do simple typos in an extra thread.
There should be a fourth category for 'mod bugs'. But i would seperate this bugs in another thread. Maybe we can've such a bug list in the mod subforum.
In moment i'm analysing the bug thread. When finished i would write a list and try to categorize the bugs. This list will be as compact as i could do it. I'll try to group bugs to one if possible. Bugs which aren't reproduceable wount be in the first run of the list. We could discuss/analyze such phenomena.
I'm not sure when i've finished a first version. Most likely between christmas and new year.