Here's another idea:

struct S {
    int arr[3];

    template <char... Name>
      requires (sizeof...(Name) == 1)
    int operator""() {
        switch (Name...) {
        case 'x': return arr[0];
        case 'y': return arr[1];
        case 'z': return arr[2];
        }
    }
};

You wouldn't need to touch using-declarations; this is pretty much
using existing syntax.

Such a "member selection operator" could also be used to implement
swizzling such as "s.xy", "s.zzz", etc.