Wow there tonto[}:)] There is a reason that kite shops do not sell that style of PFD for kiting.
Kite surfing is a fairly athletic sport it is not in your interest to add safety items designed for kayaking or boating.
Unless U are set on a seat or board shorts style harness you will have difficulty with that design.
A good design is more styled around being an impact vest - they go under a waist harness - some (designed for cold weather - really cold) go over the top with slit for hook to come through.
Most impact vests give u buoyancy but not to the rated amount of a PFD - but more than adequate for buoyancy and retain the movement factor U need.
U do not want to compromise your harness fit with a PFD designed for a different sport. I started with a seat harness and a similar PFD and ended up ditching it as too loose fitting it rode up and due to the bulk could get in the way handling my kite when trying to re-launch (I used it for wake boarding / water skiing). The big change in kite design since then has meant that you do not have to swim towards the kite to get it positioned for a re-launch...
I insisted both my kite surfing kids went thru' training period with an impact vest (and helmet).
For car keys etc - get a key lock safe (refer shop section) - or wear a waterproof pouch. By the time you really want storage for say a big down winder you will know what U R doing.
So thinking safety is good but not to the degree it can be a hinderance especially when you are learning. Drowning although a real threat is way way down the list of risk factors for a learner. (If your training / instruction has put you in a position you felt you could drown


then swap instructors / kite school). Go an impact vest especially if U want to use a waist harness. U can always wear a light weight wet suit for extra buoyancy.
Cheers
AP