The one reason that the players union would not want a capless year is a capless year also has no league minimum. So the veteran bonus would go away, and most the non starters (Or at least once you get past say your 3rd WR or nickel back and 3rd down back) might not even be offered what previously was league minimum.
That and for most of the non skill positions, as in your linemen and backers its not an apples to apples comparison for players. Most linemen who are imports who are in the CFL are there due to differences in the game make them a better fit in the CFL then the NFL (read into this typically undersized for the NFL game with more run blocking and smaller field)
So this is something I don't think most CFL fans will need to lose any sleep over. Will there be some movement back and forth of players? Sure. More then usual? Chances are no.