Yeah, I have been thinking that too. But why you want it to be based on
Ubuntu? I am interested to know why.
In my opinion Debian is a better choise because it does not have that much
trademark and branding things like Ubuntu and when it gets good supplement
repos the fact that there is not two annual distribution releases per year
can release resources to keep the supplement repos in good condition.
On the other hand Ubuntu is a little bit more polished for average user and
that average user can get more software installed out of repos (users must be
able to do what they want to do). The polishing issue though should be solved
by forking a polished version of Debian, and the software out of repos should
be solved by good supplement repos.