I know it's a bit unlikely but the issue I see with counting just salary is that a team could structure a player's contract to have very obvious 'compete' years where everyone on the team is given less than their worth to have one very competitive year.
I know it's not a perfect example... but say your entire roster needs new contracts. You give all of your star players fair value for the first 2 years, and the 3rd year they all take 1 mil dollar cuts in salary. Your depth players take a 200-500K cut. That opens a huge amount of cap space to sign other star players at even fair value.
Say this situation were to apply to the Hawks:
Toews- 5 mil
Kane-5 mil
Hossa-4 mil
Sharp- 4 mil
Keith- 4 mil
Seabrook- 4 mil
Based on their current cap hit, that saves 6 mil right there... just on the stars of the Hawks.
I know it's a bit of a stretch to say that a bunch of players on any given team will take a pay cut in any given year... but for a good chance to win the cup, I'd say there is a possibility of it happening. And obviously, not all of your players will be up for new contracts the same year... but I don't think it would be too complicated to structure a year or two where many players take cuts and said team loads up for a cup run. A calculated average (cap-hit) sort of prevents that... and honestly would be 'circumventing the cap' more than these long term deals IMO. At least some risk comes in when you structure a contract that way... I don't see too many drawbacks in my salary scenario.
Didn't really think this scenario out entirely, just something that I had thought about previously.