Just thinking about an aircraft's velocity as a specific type, rather than a vector with three floats, has my mind whirling. I can imagine a lot of terrifying things I wish I didn't think could be added later to that struct in some avionics system. What would you need a type for that for? Am I thinking too high level, where this type might include its own getters and function calls?

Think of types more as physical units to check your calculation. The position on a chess board and on a checker board are both 2d integer vectors but you might or might not want them able to be summed together, the same way that 5 liters and 5 grams are both real numbers but should not be summed.