1. There is no doubt that she will be playable. I tried to focus attention on her playstyle. Arcs just can give her Nu/Lamba playstyle but that will be too uncreative and boring.
2. I have quite opposite opinion about this. New H voice sounds like street teen. His voice is especially bad when he trying to show madness or anger. In Valk bad ending when Haz tried to kill him, he looks dumber than Tao with such voice. Older one sound much more intelligent, sly and arrogant. I know he is based partially on Gin from Bleach (never saw it) but he shoudnt be just cheap copy of him (cause Doug Erholtz voiced Ichimaru).