Is it (and if not, what technical reason is preventig from) possible to have optional fields based on generic struct value

Lets say I wanted to create a generic struct for a vector for storing coordinates withing n dimmensions. I could do a separate struct for each dimension, but I was wondering why couldn't I do it within a single non-specialized generic struct, something like so:

template<int n> struct Vector {
std::array<float, n> data;
float& X = data0;
float& Y = data1;
// Now lets say if n > 2, we also want to add the shorthand for Z
// something like:
#IF n > 2
float& Z = data2;
};

Is something like this a thing in C++? I know it could be done using struct specialization, but that involves alot of (unnecesearry) repeated code and I feel like there must be a better way(that doesnt involve using macros)

https://redd.it/1pa3d21
@r_cpp