Relay racing is all about the team and the van. In short the experience you have during the race will be about the people that you surround yourself with. With that in mind anyone can be a great teammate. There are also some types of people that you won't want to have in the van. It's really a short list of who you don't want in your van. Running ability doesn't matter, singing abilities (or even the lack of) can only add to the experience. Grab some friendds, get a van, and get out there and run!
The team isn't there to support one person, the team is there to support whoever is on the course running at that moment. Who's getting ready to run, and who just puked their guts out runnig up a mountain. Everyone will have their turn being the runner and everyone should share their turn being the supporter. The ratio is 11 to 1. For every 11 times supporting others you get to be the center of attention once.
Many people claim to be high maintenance but few will reach the threshold that will annoy all at a relay race. In general though, if you can't poop in a port-a-potty, live off of PB&J, run in bad weather, or go without sleep a relay race might not be your thing. A relay race will only allow others to learn just how much of a whiner you are.