Blood vessels can expand and contract. That's why fighter pilots without legs can actually withstand higher-g maneuvers. That's also why compression socks can improve circulation and reduce swelling in your ankles if you have to stand all day.
You just wrinkled my brain. Is there an actual group of fighter pilots without legs who are taking advantage of this?
The other thought about legless pilots is the feet I think are used for the rudder control (pedals), so there is some loss of ability to control without using your feet. While I think computers could probably take this over, in the end it does mean two less things to interact with the plane.