Most definitely (wake boarding etc)..
But i wouldn't waste too much time on it if you can't or haven't done it already

Waterstarts was a complete piece of p#ss and easy after kite control
I mentally replaced the consistency of a running 50hp etc motor with the current knots of wind and kite size at 10 and 2 o'clock etc
It's exactly the same thing really...the boat moves you(or cable-park ski) at a certain speed..so does wind in knots complementing kitesize

V easy.so waterstarts and balance etc would be easy
This is going to be great loving the small argument here ..but wasn't expecting it..
a bit like the control freak secret spot salesman who turned up at my local 10 or 20yrs behind everyone else.. clogging it all up and suddenly thinking he's God of the place only interested in 'selling' that sounds a bit familiar

R.e trainers
To be honest when I learnt I just bought myself a 2m inflatable and guided myself I found those 2line bar things pointless after about 25minutes....but...
I believe for some who are pretty clueless about it they are useful
Each to themselves I guess whatever suits whoever it is is probably the best idea...

...so maybe they can still be useful..to some extent..