On the first point, if everything is outlined clearly, I really think you're overstating the difficulty of tracking the money. Furthermore, the people who aren't prepared to deal with something like this wouldn't participate in these types of transactions.
On the second point, while it's true that people would be going over the cap, in theory, they would be compensating for that by yielding talent to their trading partner.
I think it would be a good idea, but I'm obviously OK with whatever you guys decide.