i finally get to see the fatality to your lady octopus (yeah i know, its kind of late), but i like it alot. i loved the one when she puts her opponent in her mouth (its disgusting and lovely!!!) so keep up the good work. also i just played xenosaga(epi. 1)and one of the bosses in there is a huge (yet ugly) female mermaid and it kind of reminds me of your octopus.
For a new female sub-boss, either get a superpowerful Sheeva, new Shokan to go after Noob for killing Goro, or just have a regular character depending on the character used in Arcade, like: Baraka's end boss could be Mileena; Scorpion's could be Sub-Zero; etc.