This is a big ask, but also a big help for audiobooks. especially of a fantasy setting.

It'd be great to be able to have accent relationships between an existing voice(s) and the new voice being generated. Like if during the voice creation process I could reference an existing voice and say that the accent should be similar. This would make it more straightforward to design voices around families and regions.

For example: I could say that two voices are siblings, so their accents would be identical. Or, I could say that the two voices are from a similar region, so their accents would be related. It'd also be handy to say that two voices are NOT related, and therefore help to make them distinct from each other.