I think it is very difficult to compare CBA's in different leagues due to the wildly divergent revenue structures. For example, MLB could never have a NFL type CBA/salary cap in that the majority of NFL revenue is national and spread evenly between teams coming from television rights and a revenue sharing based upon that. As such a hard salary cap which is shared by all teams can function to a degree. Though that said, the NFL has enormous problems with its CBA and is looking at the realistic potential of a) the un-capped 2010 season and b) a lockout in 2011 (now, related, I agree that the NFL CBA is incredibly problematic, is unfair to the players ((the growth of signing problems is a poorly applicated band-aid in response to non-guaranteed contracts, not a well thought out system)) and is largely a result of the failures of the NFLPA which HAS treated their retired players horribly, a system they must change).
Similarly, an MLB-style CBA also differs from the NBA though perhaps not as divergnetly as the NFL but is equally problematic. To quote Donald Fehr on the differences between MLB and the NFL:
"In football, two-thirds of the revenue is generated by national sources. One third is generated mostly from gate receipts, and you're only trying to sell out eight games," said Fehr. "In baseball, you're trying to sell out 81 games, most of them are not on Sunday afternoons, a good part of them are during the school year and you're trying to broadcast locally up to 162 games. By definition, it means what you do locally matters much more than it does in football; and by definition, you will see significantly wider spreads. There's nothing you can do about it."
Chiefly, for myself at least, I have found my interest in baseball waning dramatically as the distance between the haves and the have-nots has grown laughably large. It just isn't as fun a sport to watch when you know going into spring training 60 percent of the league has not a chance at making the playoffs, that their players will never stay past their rookie contracts, that some teams have 2 players making more than the payroll of entire other teams. The economics of MLB are messed up horribly and it greatly effects the game in a negative way. As much as I love the Red Sox my interest is severly challenged by the fact their payroll is 5 times as much as other teams in their own division.
So, per the NBA it is very difficult to say let's take a little of this and a little of that because the differing economic situations of the leagues has such a profound effect on how their CBA's are structured. I for one think going to a system that abolished a salary cap would be detrimental to my interest as a fan and to the economic success of the league (which is trouble at the moment, granted). The "soft-cap" of the league now provides a structure that isn't hard, and allows some flexibility, and the luxury tax punishes and deters MLB style rampant spending, which I find to be a good thing. Yes, it is overly complicated but I think changes to the CBA have to be minor ones within this system not a drastic overhaul based on a NFL or MLB system.
These are somewhat general thoughts but I have rambled for some time so will hopefully add some more specific thoughts later.