Yeah I agree with Ray's issues with buyouts. It would restrict movement on fringe players, take certain players that still have some value completely out of the league. Also we'd be punished for mistakes real life GM's make. There would have to be some kind of grace period where you can release a player that signed a new contract without penalty.
From a practical standpoint though, I just think it would be a lot to track. The cap is easy because it matches the NHL. But with the activity in our leagues there would be a lot of buyouts, and a lot of dead money, for a lot of years. Not even just big contracts, but just dumping depth players in season. For example if you have an injury in season, and pick up a replacement player that might have a 2-3 year deal, when your player comes off IR you'll have to buyout the replacement and take a cap hit for a handful of years. Every single time a player is injured. There would have to be a minimum salary as Ray suggested as well just to avoid the paperwork.