I use half fleshed out ideas and basic pairings in mine. Because if I do fully fleshed out ideas, I run into the issue where person 1 wants to do the idea. We're working it out. Someone else requests the same plot. I tell them it's already taken. I start the thread with Person 1. They ghost after 2 posts. I tell Person 2 the plot is open now. They say they don't have any slots available anymore. Now I have zero RPs.
Since you know what you want to play, why don't you just brainstorm a couple of setups that would work for that character? Then post the character sheet for them alongside a list of potential plot seeds. They don't have to be longer than a sentence, lol.