Pretty much, yes.  Firewalls are designed to stop you.  You might get somewhere but it's a lot of work.  And then fall back to relays.  So right tool for the right job.  P2P for some small things, relays for bigger things, http for largest things.

Simply ask yourself, in 10 years time is amazon going to switch to P2P?  Is facebook?  Is google.  P2P is a good tool, but wont win.