Although i see your point in worrying that the different reasons for wanting to get at the magic item might lead to intra-party conflict, Rigamortus, I think that, if they're not used as a way to BRING the group together, but thrown in at a later time, they can also lead to interesting interactions and no hostility.
Paladin:" No way! For the umpteenth time, the ritual contained in that tome is too evil. It must be destroyed."
Rogue: B-but.. but we'd get a TON of money. I mean, if you can just relax a tad on this, I can just accept to give an extra percentage to a charity, or your church directly... I mean.. it's a LOT of money you know... really lots..."
Wizard: "frankly, you know me, Pallie. (Ain't Pallie a GREAT name for a Paladin? Like Reggie the Rogue and Wizzie the Wizard?) And you know what I am looking for in that book isn't evil. Not in the least. And I think..."
P : "I know YOU are not evil! but the tome is a temptation. And if not destroyed, even if we used it soundly - assuming that can be done - it might be stolen, taken, copied. And then, we'ìd be responsible for the evil that was wrought."
W: "What if we used it to GET the guys who want to do evil with it?"
R: "er, like how?"
W: "I copy the part I need. Then we make a fake copy of the book... I can study the ritual - under supervision from your church, Pallie! I was getting to it - and make a flase copy of it, flawed so that it doesn't work but close enough that it isn't apparent at first glance. Then we destroy the original copy and have the false one delivered to your "customers", Reggie."
R: "me deliver a FAKE? and then have them all on my trail?"
W: "Sure, Reggie... like you don't have half a dozen alternate identities you use when dealing in-"
R: "Ok, OK, Wizzie - No need to go into that, I got it.".
P: "I still don't get how that helps us GET them. they'll probably send a middle agent to retrieve the book!"
W "-sighs- Sure. but we can have a spell cast to trace the fake book. It'll lead us to their REAL lair - and in the meanwhile, while they find out the ritual is flawed, we can even muster our forces, gather some intelligence. How's about THAT? I'll even accept to have my memory of the exact evil ritual erased from my memory, Pallie. I really don't care for that, you know me, we've been risking our lives together for years. I only need the OTHER info."
P:" .... I have to talk to my superiors at the church about this, but... it's not a bad plan..."
.... just an idea that came to me. Different goals can lead to something different than violence, and still all get solved. It's a matter of players PLAYING. and in no way having a quest card hampers this, on the contrary, it makes them think more on HOW TO GET what they want.
My 2 cents, as always.
