Quite a large order I am aware... but perhaps we could borrow some code from the bittorrent/utorrent projects?
One of the problems that torrents faced a year or two ago was "throttling" or traffic shaping by ISPs. Read: meddling with consumer's software programs via the net.
If I am not mistaken, the port randomization and traffic encryption abilities of torrent clients got around this.
Perhaps constantly rotating ports would not be possible without some sort of centralized tracker that torrents make use of? But surely it would be possible to eliminate any "signatures" that bitcoin might leave in it's transmission messages by encrypting the data.
Would be very handy to have one single framework for p2p applications that would handle all this stuff...
But before it's done and before all p2p networks are migrated to it... ;-)
You can use bitcoin via tor, there should be several nodes available as a hidden service.