I'm a bit confused by what you're proposing, but I will say that the problem with fat pointers is they are incompatible with existing compiled libraries, meanin

I'm a bit confused by what you're proposing, but I will say that the problem with fat pointers is they are incompatible with existing compiled libraries, meaning you usually need to recompile absolutely everything (including libc). There are only limited circumstances where this is acceptable (or possible).