I'm sorry, I do not think clowns need a new donation weapon of any sort, they are the epiphany of annoying. Tarot casts so many negative side effects on an enemy, and Arrow Vulcan is powerful enough as it is. I play clown just as you do, and I don't think they need an upgrade by any means.
On the Assassin Cross Katar, I can agree with making an updated, more powerful version. I do not agree with making it 1 hand however, but maybe extending it a 10-15% damage reduction would be OKAY. Nothing close to having an Usakoring Shield equipped, but giving them SOME survivability.