In good things you said "1. Support for all Debian-based distros" and in bad things you said "2. No ready-to-go commercial drivers support.".
But if I understand you well it would be in a separate debian repo equivalent to a PPA, so it could be installed on ubuntu. Am I right ? If yes how should I worry about how would it be different from the current ubuntu based KXStudio ?
I mean whatever the base (deb, rpm, etc), whatever the distro name (ubuntu, thingamabob, bestdistro, nooblinux, etc) I currently go for ubuntu because of how easy it is to install / maintain / use / works out of the box / etc. If you tell me I'll still be able to have all the latest audio softwares I have now on the next ubuntu just by a slightly different way (from a user perspective) I wouldn't see why I would vote no.
On the other hand, if not, I would worry a little bit more