Such situations can happen in other sports where this is used and also everywhere else, work, relations. There are mechanisms how to deal with it that can be contained in the agreement like terminating the agreement in the cases 1., 2. ... X. abusive behaviour etc. (it's also part of why I say "it would protect both sides, the skater and the coach"), it's nothing new, no need to reinvent the wheel.
I’ve seen firsthand when a student and coach cease to be compatible with each other. I’ve seen coaches refuse to work with a skater (actually often times it’s the parents they don’t want to work with) and I’ve seen skaters who no longer respond to coaches or lose faith in them. These are not situations I believe would create positive results for anyone involved and I’m not certain a contract would suddenly make these situations manageable or even safe let alone productive.