You would get more leverage if you participated to some already existing client, with a proven ability to scale and evolve.

My favorite right now is gtk-gnutella. Although it is written in pure C, the new maintainter/author writes very good C (I've learned a lot reading his code) and he documents nicely what everything does.

I'm thinking about a few areas where I could contribute usefully myself.

Did you try to contact the author before jumping into writing your own client, which is a pure waste of human effort? How can the open source community compete with LW and BS if we disperse that way?