Hallo!
I expect some object classes to not be really separable from the core, and I don't necessarily mean DSP: think of [inlet], [outlet], [pd]...
However, I expect 80% or 90% of the internal classes to be externalizable. Let's do it for those classes first. Reuse the work of PDa if it makes sense.
just an other thought: if there is a lib for audio, math, ... (as you proposed) it would be really handy, if also the externals are somehow organized in such libraries, and not by name of the authors ... (I know this is not so easy to achieve, would require a reorganization of the cvs, ...)
anyway, I think this would also be much easier for users and would prevent developers to double things, etc. ...
LG Georg