In case anyone is interested in running two Tor instances (regular, bridge, relay, exit) on one machine, I've successfully made an init.d script to do just that. From searches on Google it looks like others have asked about this in the past, so I'm sharing this for them. Tor only allows two Tor instances per IP. When the TBB came with Vidalia it was much easier to casually run a couple of relays per IP, but with the service it's a bit more tricky. Nevertheless it is possible:
Instructions are here: https://gist.github.com/Jesse-V/11007048 Tor should be stopped and be sure to make a backup of /etc/init.d/tor before doing this in case things go south. Be sure to set up the folders and separate torrc file before replacing the /etc/init.d/tor script. The commands will be the same as before, so "service tor start" launches both. The script is a fork of the one that's packaged with Tor 0.2.4.21.
Use your own judgment with this, but I'm just posting this for anyone interested.
Jesse V.