I don't agree that banning kitesurfing will solve all spot-sharing problems. On one hand, we do have beaches that are forbidden for kiters because of trees, nearby roads with lots of traffic, etc...Just use some common sense if kiters want to launch from a beach.
On the other hand, I have lots of friends who do kitesurf and have never experienced a problem with them. The reason is very simple on our lakes : kitesurf have zero priority rules over other sailing crafts, windsurfer included. This means they do have to pay attention and be extra cautious about any other users at the beach if they want their sport to survive. In practice, however, each rider is paying attention to the other and I tend to let them use as much needed space as they want. The only exception is in waves where you need to voice yourself quite louder if you want to catch at least a wave when it's overcrowded...
Just a couple of comments as well about kitesurfing or windsurfing on lakes :
1) you can go kiting in about 7 knots of wind providing you'll have a fairly big sail (20+ m2) and a kiteboard that is longer than usual. Reason is you need to build quite some speed to go forward at a reasonable pace and not just going stop and go with a short kiteboard.
2) 7 knots is the lowest planing limit with a Formula kit.
3) below 7 knots of wind, longboard windsurfing can be exciting and challenging providing you have the right high-performance gear to excell in those conditions (long and slender hull coupled with big 11 m2 sail).
Kitesurfing is a no go, however, mainly because it's extremely difficult to get the giant sail out of the water in say 5 knots wind. You'll need a helping boat to unstick and fly the sail again. And you'll drift anyway with the wind. A big kiteboard with positive floatation is of no help in that case.
Because I want to maximize my TOW from 1 to 40+ knots, windsurfing is plenty enough and up to that job so far.