In my Perfect Programming Language That Doesn't Have To Deal With The Problems Of Actually Existing, serialization of data structures into memory is explicitly defined in the language, just as one would define a JSON or Protobuf serialization. One could define a "Point3{x,y,z}", and hypothetically define one array of them in the conventional manner, define another array as a columnar serialization, and potentially even define a compressed data structure right there in memory if that was advantageous.

It opens a wide array of exciting problems and possibilities, if you start thinking of that as something a language should let you twiddle with rather than hard coding it. It seems like a lot of high performance stuff is moving in a direction where this would be advantageous.

(For example, if you compress an array, you lose random access. The language would have to carefully build up capabilities from scratch so it can have a concept of "arrays" that can't be randomly accessed, can only be written in some very particular manner that may even require a "flush" concept, etc. My gut says it ought to be possible, since, after all, we can do it manually, but it would be a very careful operation to disentangle casual assumptions about what data structures can do based on the definition of what data they contain vs. how they are represented in memory, and what capabilities you get from that.)