In terms of worldbuilding, there's no reason there wouldn't be female musicians doing phantom lives, if that's what you're asking.

This is extraneous rambling:

I know that some serieses do go out of their way to justify why the entire cast is male-only, or at least majority-male (obviously there's Hypmic's gendered worldbuilding as a comparison, since Paralive can never escape the comparison; but also things like Visual Prison, or even just the single-gender justifications for franchises set at schools), but Paradox Live doesn't.
The only reason that the entire cast of Paralive are men-and-Anne is, related to the last question I answered -- just because the series is aimed primarily at women who want a cast of ikemen, and so everyone who is participating in this one music competition just happens to be an ikemen (and Anne).

I think it's also good to remember that fact, just in general; remember that the story of Paralive is not really about huge world-changing events and winning doesn't confer, like, political power or whatever; it's just a music competition, and the phantom live music scene exists outside of it.