I never ever ever see anyone use the definition that the ma'oste seems to assert, which is is that it's in UI*5, it's a modifier. Even though no one ever ever says that I obediently rationalized that in the Lojban in my mind. In my mind, people say "ju'o" all the time because they're always eliding a UI before it, possibly ".ia" or "je'u" or something. Yeah "je'u" feels right. I always imagine, ridiculously enough, that because the ma'oste says it's a modifier, that what people mean when they say "ju'o cu'i" is actually "je'u ju'o cu'i"-- that this is the truth, I'm of indeterminate certainty.
I don't care how we rationalize it. If I can't have one syllable that means "maybe" I'm going to take one of the two-syllables, there's plenty left in the CVV'V shape isn't there? No reason why not, no reason anymore these days.