Everything you mention would be possible as an addon to the current ULX (except maybe XGUI theming). Why not focus on that? I do want to give our backend functions an overhaul at some point, but
throwing code out is generally a bad idea.
So I guess the bottom line is, that you ask us for our support, and we're willing to support these ideas as addons to the current ULX. We (the team) quite like the light, robust nature of the current ULX. It's not perfect, but it gets the job done.
On MySQL, I think you should totally go for it. It's a frequently requested feature that we've never really comfortable supporting with reliance on a third party addon. UCL was designed with this kind of thing in mind, so you should find it fairly simple to implement.