I’d start from allowing multiple mutable references. Second would probably be something about relaxing lifetimes but I can’t properly articulate it right now.
>>giovan+(OP)
Start by allowing anything at all: not ignoring it, but reporting it. And continue reporting it, until it is wrapped in "unsafe" or fixed.
It would not be a mistake to report the total number of "unsafe" blocks harbored in the program when it is linked, from all sources, alongside the live borrow violations. Safety, like development, is a process, not an endpoint.