Change to std::array now, deal with individual std:: vector cases later? Or is that change for change's sake?

The only change where std::vector would remotely make sense is the singular use of AutoFreePtr, but an uninitialized chunk of memory is fine there.

Everything else is a simple, static buffer for saveload. A plain old C array would do the trick, but std::array has the option that it might not use the stack on system which are limited (I don't know of any, but except for a few more source code characters, I don't see any disadvantage from using it anyway).