Three problems with your plan.
1. If you use the Belle's slow to Die 1 action to sacrifice her, she will not drop a Corpse Counter.
2. Rule of Equivalency states that you may only place one unit for your Belle's death, meaning you'd have to chose between Bete and Killjoy.
3. Although Soul Stones for Seamus are more of a commodity than a necessity, the cost of a Bete + Killjoy crew will leave you with very few units.
Killjoy has a decent survivability and Bete can be technically invulnerable but the trio of Killjoy, Bete Noir, and Seamus with the possibility of another Belle do not a long lasting crew make.
Perdita, for example, would rip you a new one quickly, very quickly.
Realize also that Black Blood would damage your units as well because they are not Neverborn.
Your best bet would be to simply drop killjoy from that list and pick up Belles and the possible addition of your Copy Cat or even Sybelle.
Though, due to the sheer massive damage output that crew would have, if you could quickly drop your opponent's master, things may go smoother.