I'll have players rolling only a d4 at most. Only to determine success or failure. It wont become a stat vs. stat.
In a world full of, "I'm awesome, the center of attention, AND the main character" players will appreciate having the chance to actually earn something. To be able to brag about something legit other than, "yeah I killed an NPC that *I* created and got this cool item/weapon/side-kick." Where as if I create it, and pin you against it, then you and your character can actually and full legitly say, "Yeah, I had to put my character through hell."
Granted, as you've already said, you weren't keen on it. For me all that means is that there's one less person to think of stuff for.
As for everyone else, you're always welcome to join.
Now as for the two arrancar that have shown interested, do you two know each other at all?