Unlimited VAR will slow things down and be annoying. I'd like to see them try it on a challenge-only basis, with a limit on the number of challenges a team could use, not per game, but per season.
Say each team gets 5 failed VAR challenges per season, no more. If you challenge a call and your challenge is upheld, you don't get charged for using one. That way, every time a team is clearly on the wrong end of an important call, they can challenge and go to VAR, but they shouldn't waste everyone's time challenging a call that really isn't important in terms of their season as a whole. If you challenge too much and you're incorrect too many times and run out of challenges and can't use one late in the season, then too bad, that's your own fault.