The real problem with taking up another sport is how do you want to spend your time. If you are keen on SUP, kiting and windsurfing can be a distraction to the main game. You really need to push yourself to drive down the coast to surf if you know that a sea breeze is going to hit in the afternoon and you can go kiting or windsurfing. The bottom end for kiting pushes well into the top end of the fun wind range for SUP. Are you going to want to paddle into a 15 knot breeze when you can be riding and jumping?
You can get a sailboard rig to attach to some SUPs. They are designed for small sails and flat water cruising. Starboard explicitly tell you not to jump them.
For kite safety, most of the fatalities come from people being pounded into hard objects like rocks and seawalls and reefs and breakwaters etc.
The early kites were very powerful, had minimal range, an inherent instability, and dodgey safety systems.
The kites would do something bad (either through being set up wrong or through instability), recover, then slingshot the rider. If there was anything hard in the way then the rider would be injured or killed.
Modern kites have full depower on the bar. You just let go of the bar and the kite spills sufficient power for you to either ride out whatever is happening or go for the backup safety. Most kites have three levels of safety, push out the bar, release to a flag out leash, eject the kite completely. In 10 years I have never had to use more than the basic safety systems. It might be different for you.
Self-launching and self-landing is easy. You just have to learn how to do it. WInd changes and dropping off are also not a problem. You just learn how to deal with it. I swim in a lot less with my kites than I ever did with sailboards (actually the last time I swam in was 27 February 2005

I keep a log book. ). Kiting in the surf is huge fun and way easy. You can jump off or over big waves or smash them and run away if they are about to clobber you.
As Dean points out, you can kite on any kind of board you want. I learned on a 9' mal with a stunt kite. I now have (or have access to) twintip, kite surf, kite race, surf and SUP boards that I can play on with a kite. I've ridden sheets of ply as well. All good fun.