Service height- some of the top Asian players in MD are 5 foot 6, (168cm), some of the Europeans are 6ft plus (184+), so even within the current rules some players are serving 15cm higher than others, yet we still see many shorter players winning, so its not a big issue. Of course some service judges are not as strict as others, I think the constant delays are the bigger problem.
ANy solution involving a set height and technology would of course be unworkable at below national level, so you would have 2 sets of rules, so I wouldnt be in favour
You can't prevent mopping, especially if a player dives....
This one is tricky. I've seen players dive for a shot they know they can't reach, just so they can get the floor mopped and slow down the match. But how do you prove it was deliberate?
The current rules do allow umpires to penalise players for deliberately delaying the play (16.6.1). But the rule generally isn't enforced. I can just imagine the arguments if umpires suddenly started being strict about this.