I used an old roadbike for a few time trials a couple of years back and just ran a 52 ring with no mech or chainguides, standard 8 speed setup at the back. The problem with this setup is the chain can unship, it didn't happen to me but I could've just been lucky. It wouldn't have been a big deal in a TT* but it'd be a shoot if it happened in the bunch.
You can get chainguides- basically flanges that bolt onto the sides of the cranks. Sometimes these are used on cross bikes (try Salsa cycles, they used to sell them). A lot of these are made of carbon now and they can be a bit pricey- should be possible to get alloy ones tho'.
You could use two or perhaps another option would be one on the outside and a chain watcher on the seat tube- unless the tube is an odd shape or something.
It's possible, I'm not sure whether it'd give you much of an advantage. You'll save a bit of weight overall I guess.
*Obviously it wouldn't have done my time any good, but it was unlikely to be especially dangerous.
