It's quite simple, instead of letting all players have /fix or simply restricting it from all users, allow for the mending enchant to somewhat replace /fix. If it proves to be too much, a nerf on repair speed or exp cost would be easily completed by techs. (Should be able to reduce speed via changing the durability per tick)
*disclaimer: I haven't had access to my minecraft account for weeks, so I have no clue how fast the auto-repair is and how much exp it uses. Also would have to be put off until the server officially updates to 1.9
I do believe that this could be used as a halfway-point, and even better, it's a normal enchant which would be EULA compliant
