I was late to the main discussion, but i want show you intresting
thoughts from one of the oldest DD:
http://blog.liw.fi/posts/debian-developing-it-wrong/

Some items (deb-internals related) very hard to implement without
partly/complete loss of compatibility.

* smart build tools
* debian/rules clean
* ucf -> dpkg

But some of them should be easy to implement, if you will build your own
infractrusture "from scratch":

* VCS
* large scale changes (for your own repos)
* mass building (wanna-build has terrifying install process and total
lack of documentation, pbuilder is too 'personal' and can't handle repos
of 'overlay' type without hacks)

Good luck.

-- Alex