That sounded like a Lego approach. :)
So the way I see it the GUI development should be in the most seemless way for the user, right?
And we also have the problem between people who prefer a simple, leaner GUI approach (the classic PD, for instance) against people who prefer a more sofisticated, and sexy GUI. And I believe both groups would also like some more knobs and stuff...
so basically, we should at least have two options of gui: simple (classic) or sophisticated (sexy). But it would be cool to make it open enough to anyone develop their own or come up with new and customized ones. that would make PD way cooler than Max/MSP or anything else. So for that to work (and now I must admit I really don't know the architecture behind this part of PD, so maybe it is already this way), the comunication between the GUI and the rest of PD should be kept simple, fast and modulated, working with the leanest possible API. I also think this is a good approach considering that most of these toolkits will stop getting support way before PD ceases to exist. I have also thought about the possibility of skins, but then loading a bunch of bitmaps would not help in terms of performance...
At the same time we pick a toolkit and focus on that one first. So we should think of at least two teems, right? One at the GUI end and the other at the core PD end...