Can there be unlimited DRS ?. …and if so, will it be time consuming for officials!
If one wants to improve the game, than criteria should be to maximise technology.
Let the 3rd Umpire with reserve umpire do more work, viz take calls on wrong decision made by on-field umpires, and ask them to revert.
And at the same time, take away DRS appeal from players. They cannot decide whether they are out or not.
Today, all broadcasters are well equipped to the standard requirement in taking care of DRS technology. It takes less than 20 seconds to replay the previous ball bowled, from which one can make out whether it was right or wrong decision. The criteria for fielding side is to appeal, than its upto umpires(all of them) to decide on the decision.
I am certain there is a constant feed on various required angle for 3rd /reserve umpires in the box, from which they can find
1- no balls bowled
2- low catches
3- rope catches/fieldings
4- run outs
and many close actions.
I certain if this takes place, we would have zero error.
And as far as on-field umpire getting slack, than points should be given on number and type of errors made by them, which should be their performance evaluation. The lesser the errors(difficult ones), the better umpires.