Not sure how well GW would take that. They can be quite protective of their turf, especially the miniatures side.
Convincing GW to make figures of the U5 (maybe even with a bit of profit to FS) is a different matter. Technically, they’re part of the old universe that’s been dead an buried for a while now, but AoS versions of the U5 could well be reasonable. Or a limited edition of some kind, as was suggested. Might get easier if we get our steady playerbase up again, so that there’d be a certain significant fanbase as ready customers.
I think (but don’t quote me on this; I don’t know the legal side) the easiest way would be for a volunteer hobbyist to design the sculpts for the minis and release them for free, as 3D print templates for anyone with the resources to use.
That said, these would be some of the few miniatures I’d actually consider purchasing, just because.
Then again, I’m certain some people have already kitbashed them together (and could quite possibly provide a parts list), as I think that appearance-wise, they’re quite typical for their Careers. Kerillian has her masks and several other Careers hide their faces behind helmets too, so there’s not always even extra facesculpting to do.