I haven't played TAY--only the OG-- but holy shit do I love this. This is beautifully written; dark and wistful and tragic. I've always had a huge soft spot for Rosa/Kain, and it's because of all the reasons you've beautifully fit into the subtext (and the gloriously overt!) here.
Re: "Never Meant To Let It Die": FFIV, post-TAY, Kain/Rosa, G