children, behave.

first, cssu-extras would only provide packages dependant on features introduced by cssu. Take cuteTube as an example of what to do, it just looks at version and enables features if its installed. That way it remains compatible with stock 1.3, as was always the intention. Only "extras" development worth looking at IMO is regarding building for thumb in addition to basic armel and i386. Currently only a few extras sitting in the thumb repo or forum pages exist.

mp... package is useful for updates, sort of one package to rule them all (or update them). it ensures all packages are kept in sync and it reduces fragmentation of having multitude of versions of one package installed on different devices. this is fixable to an extent with >=package-version.x.y in each dependency.

in the long run it could be stripped down to focus on core system and drivers etc, freeing file manager, modest etc to be removed from it completely or using a virtual dependancy fullfilled by the package of your choice using "provides". Hardware wise, I've already suggested using virtuals over in Neo900 porting thread to allow for device specific packages. freeing filemanager, modest etc is both a blessing and a curse. you can update them independently for quicker fixes but could then end up with problems with packages not updating to bring in fixes for changes introduced in core packages.

whatever happens, your going to need to maintain an upgrade route from stock. this could be a mess of pre/post install scripts to protect packages from accidental removal.