Sounds like a good plan. Paperwork and giving yourself an out sound like the way to go.
As a teen that didn’t have their own horse, ride options included: saintly old schoolies with restrictions, BO’s flip horses (fresh OTTBS/OTTBs that flunked out of polo training) and precious show horses owned by AAs willing to head the Pet and Pay Department. That scenario is about the only thing that has stayed consistent in the local barn culture over the past 20 years. There are some other threads where the lack/price of trained, athletically capable horses and how that impacts up and coming riders and the equine industry as a whole are discussed. Heading the Pet and Pay Department for a developing rider is a noble position.
I dunno what your current program is like and this is kind of a tangent, so maybe not terribly applicable.
The times I’ve had someone else up on my homebred have been very positive. It was incredibly useful both to watch him go and to have dialogue with the person in the tack. If your program currently includes training rides that you watch that might not be terribly relevant other than the different perspective of another person riding.
It was also a blessed relief from managing his green butt without the guilt of horse not getting worked. Win win, pass the champagne.
I think it’s valuable experience for horses to go under multiple riders, presuming appropriate skill level. Green horses may react interestingly to different rider habits creating good training opportunities. Blah blah
Bonus the Pet and Pay Department is AKA the Calling the Shots Department. There’s security and comfort in that.