If they were starting from scratch I'd say a 50/50 split is fair, then build the other concessions around it. But that's not the background for this negotiation. The players have conceded on the luxury tax being more oppressive, shorter contracts, lower mid level exception and 5% off the amount of revenue they were getting from the last deal. That's quite a bit to give back, so I'm thinking the owners should take the 52% now and hammer them for the remaining 2% in the next deal.
Regardless, I hope Arenas and Reshard Lewis aren't heavily in debt, because they're not going to see dime one of their remaining contracts. It'll be an interesting free agent market when all the amnesty cuts are through.