Mika is pretty much as close to Tonami as you can get within current Yukigumi, actually... I personally like Nacchan a little better, but that's a personal response not anything involved with their talent levels. Really though, Mika is amazingly a mini!Tonami, but isn't so much a clone that she doesn't have her own personality.

I 100% do agree though on the fact that I also wish they'd let the musumeyaku mature a little more before promotion... considering that your voice doesn't mature until late 20s/early 30s, the years of beautiful vocal music we're being forced to miss by musumeyaku aging out of the system through promotion or lack-thereof lately just sucks. :(