The musou/warriors franchise is simply perfect for solid spin-offs.
Add a little mixture and changes like in Dragon Quest Heroes and you got yourself a great spin-off.
Hyrule Warriors is fun as hell too.
I want more Warriors spin offs, like Final Fantasy Heroes or even a Pokemon Warriors game.
Even a Dark Souls musou with the best franchise bosses as playable characters would be cool, lol.
And Solaire too, of course.