That may be true if your goal is to advance programming language research, but if your goal is to extend a language being used in industry then you don't have the luxury of spending that sort of design and implementation effort if you suspect that the extension will be a boondoggle (especially since backwards-compatibility promises mean that you'll be forced to support those features for the rest of time).
I wonder if Rust's compile-time meta-programming can be used to implement 'pluggable' linear-types for experiments, maybe along the lines of [1]. That might be a good compromise.
I can offer no proof but I'm Pretty Sure that one could hack together linear types using procedural macros, though I can't posit how nice they would be to use nor how well they would interact with the rest of the language and ecosystem.
Wouldn't that be a good path: start with initial experiments based on types-by-macros, and see how well that works. Can't be worse that C++'s template meta-programming.
