This kinda reminds me of a friend a few years back who was hell bent on using a mono ski to snow kite and in his head it was gonna be so much better........ it wasn't
Re inventing the wheel is a habit in any sports infancy, but we are way beyond that and the evolution of the harness is in the direction of minimalist custom ergonomic support i.e.. https://shop.ride-engine.com
A climbing harness is designed for you to sit in while a rope going straight up lowers you down. There are moments of that in kiting, but the vast majority of time the pull is at a much lower angle, is highly variable, and there is dynamic work being done by the arms and upper torso. In a climbing harness under those loads once you fatigue a little your going to nutate at the pelvis and round out the lumbar spine into a slouch or against its natural curve. You might not hurt for a good long while, and for some it may relieve back pain at first, but don't kid yourself that its good for you long term. A neutral pelvis with a natural or lordotic lumbar spine is THE preferred position for comfort, longevity, power, and mobility, regardless of the activity.
The pros don't use climbing harnesses for a reason. The only ones I could see experimenting that route are the racers, and that is an ergonomic mess to begin with. Foils look like they might just take all that over and help save a few thousand lumbar discs in the process.
For most a waist harness is the answer. For those whose body shape and high kite position are not something they will ever overcome, a waist harness with seat or straps to prevent it from riding up like Mystic, and Ocean Rode make are the better option. Nitrous shorts definitely compromise the spine when the kite is flown high enough for long enough but its rather obvious they are a compromise for fashion in the first place.
You can certainly stick with your climbing harness, but use it for another 15 years of hard riding and you might find you are the one who is missing out. Mobility, bladder, and bower control, these are things I plan on keeping to the bitter end.