This is Stoneforge Acolyte all over again. Sometimes, missing a couple words is the difference between insane and wildly unplayable. ^^
I haven't tried Palace Jailer yet, but I'm including it in the next update. That said, I think the other ones could work in certain cubes? Man, this is so hard to evaluate without seeing it in play. You both need to be able to defend the crown AND be able to get it back once stolen. I'll report back once I get some playtime with the Jailer.
I have been running Palace Jailer and Knights of the Black Rose, and while I have seen Knights get picked a bit more, I suppose both are pretty good cards. Knights is big enough to deter attacks, and, in a b/w control shell, he will usually take over the game relatively quickly because the opponent won't have creatures to attack with. It is, however, very prone to blowing up in your face. Giving the aggro deck 2 or 3 turns of being the Monarch usually gives them enough of a lead to close out the game with burn or removal of their own. Interesting cards, that's for sure. That's why I like running them.