There are already a couple gc libraries in rust. I wouldnt say Go is strictly "pluggable gc" since...well you can't get rid of the gc. You can try and keep it from doing meaningful work but thats quite different than "RAII managed memory with a fallback to a gc library that targets my particular use-case"

Fully agree with you that GC should be abstracted away and used for where it shines: cycles and graphs!