> Does a service like this already exist?

Its how the french navy (used/experimented with) to do uniforms.

You'd stand in a room, they'd scan you using structured light (I think, this was ~2000) then they'd extract the key measurements. However, instead of just in time tailoring, they had a bunch of trousers/shirts/tops/jackets in common sizes based on the population, rather than pattern type.

This allowed quick mix and match without manual measuring. It also allowed sub sizes to be used