you know, this is a rather big problem. while there is already a severe imbalance due to country, market size, media presence etc, this one basically distorts the practical cap value. but yeah, not sure what they can do about it.
It's actually not that hard, the league basically could take the worst tax market and make sure every player gets taxed that one way or another. All the extra cash they earn could be given to the NHLPA for retirement funds or something like that
So basically
We have 3 players all getting 1M
Player A lives in the worst tax market and gets taxed 500k
Player B lives in a market that he gets taxed 400k
And Player C lives in a Market that gets taxed 350k
Player A owes nothing to the NHLPA retirement fund, Player B owes 100k and Player C owes 150k