I think a bunch of single-purpose mods built using a general framework would be better than any other alternative. rather than something like RTB
for instance the framework could provide things like notifications, easier GUI creation, preference management, and other really basic, widely-needed stuff like that. probably a mod manager too, although it could certainly be argued that that should be a separate mod as well. but things like chat, friend lists, and any other mod that could use those basic functions should be separate, completely optional add-ons
that's the way I'd do it anyway. seems much more flexible to me, and more importantly makes it very easy for a user to customize their environment to exactly the way they want it