If you mean the free packages, then yes, we should ideally use the Debian versions and, if Nokia has not already done its job, send all Maemo-specific patches upstream. If you don't want break your N900, then you have to repackage the Nokia binaries. otherwise.....you're refering to the existing Mer project, which has only limited support for the N900's features. You basically plan to continue porting Mer to the N900 or even to repeat the failed Deblet experiment? you mean the project you have in mind? I disagree.
The project I have in mind should start with a working Maemo5 and continuously turn it into a Debian or Ubuntu derivate with as few as necessary binary Nokia packages. The result would be a "Maemo5 done right".
IMHO a wiki or homepage with information for developers and end-user as well a bugtracker would be necessary as well.