Umpires should have their own TV screen
Most umpires are just not very good at deciding whether a point should be replayed or not after a successful challenge. Why not give the umpire the same replay they show on television? The umpire could get the footage while the challenge is being made. The umpire could also use it to decide whether to allow a challenge or not.
In general I think many umpires struggle to use the challenge system in an appropriate manner.
1. They allow players to challenger after checking the mark or consulting with the coach.
2. They call let too often instead of declaring the shot a winner.