I wanna start a new RP but need helpp

ok well im currently involved in two RP worlds.

Pandora's Library
&
Welcome to Wonderland.

and I wanna start one of my own but i need some oppinions.
I have basically two Ideas and I cant decide

Black Butler RP :P were we have butlers and masters. you can be whichever you want

or

A slave RP . were theres slaves and slave owners. The slaves are gifted and the slave owners are Vampires who use the slaves as blood banks.

ummm I also need a co-owner too lol. Ill be making a serperate account for the RP's and ill give the co-owner the information too the account also.
Sooo if ur interested or wanna give ur oppinion just message me or comment

End