If I were a player, I'd be furious to be tagged. That being said, it's in the contract that you agree to play under.
In a profession with frequent union negotiation, I will say this. If one party wants to change something that is to the benefit of the opposing group, it would likely only happen as a result of some concession elsewhere. So I think the question is, what would the NFLPA be willing to part with in order to reduce a team's ability to us the franchise tag year after year?
Otherwise, it won't change. I don't know the negotiations well enough to know what they have that they could no longer deem necessary or may find less important that they'd be willing to separate with to get that done.