If someone were to submit a proposal for a single sex play, I think I'd consider it based upon it's merits (regardless of the gender).

I'm not sure about soliciting a same-sex play, unless you wanted to do something specific, such as doing two one-acts, one having a male-only play and then follow with a female-only play.

Or if you wanted to do something completely different, how about a traditional Shakespeare play with an all-male cast for the first act (the way the plays were originally performed), for the second half switch to mixed cast, and then for the third act, an all-female cast?

For each act, you could make it easy for the audience by having each character wear the same clothes even though actor playing the character changes.