There's no law says that switches can't play with one-siders; in fact it may be safer, particularly if you're after long term D/s rather than quick role-play games. I know switch couples who can change back and forth at the drop of a whim, but they're rare.

If you want to find a Domme and a sub (and why not?), it's probably a lot easier to look for two different people than to try to get them both in one economy package. I would advise being totally frank about your situation, simply because lies, however well intentioned, get in the way of real relationships. A few people (as you will see on other threads) simply can't relate to someone as a Dom if they know that he also submits elsewhere, and likewise, a few female supremacist Dommes might feel that a sub who also dominated women didn't have the right attitude. But there are plenty of people who won't have a problem with it, so why not keep it simple and honest?