The .parent field in the SubArray is specifically referencing the original internals array. And SubArray is immutable so I don’t think you can change that after it’s constructed.
Why not roll your own type that does exactly what you want? SubArray isn’t very complicated, just built the parts you need into GS.
To expand on this, if you have some field that is mutable and can have a different array swapped into it, write a view field that works like SubArray but references the container field, but accesses whatever array is in it just like SubArray accesses the immutable parent field (I assuming thats how SubArray roughly works)
Edit: you will also want to put parametric types on those structs, type instability might be another source of allocations