to be more platform independant, I think the bug tracking system must use web browser to manage IHM (bug filling, bug track, comments...)
It should use XML technology to evolve as needed (by user).

What I find important is to be able to associate comments, docs, pictures with the bugs resolution system : user could send a picture of the problem, developpers *must* write documentation for important bugs and we need all this stuff to be linked with the original bug input.
Moreover, I think a bug search engine is important to check bugs of same category/priority ... & check if there are not linked to a same global problem (so that several developpers know they're working on a part of the main problem)

In future (?), the system have to keep track of which software version correct which bug. And it should be easy for developpers or project manager to edit a list of all documents (comments, docs, code, pictures) related to a set of bug.