In the US, if the toilet had a seat belt, would it be legal for an airline to board one more passenger than the number of normal passenger seats, requiring that whoever used the toilet last must remain there until the next person needs to use it?
Inspired by: "A new engine inlet reduces vibration and cabin noise, the lavatory receives a belted seat allowing a fifth passenger and the Garmin G3000 gets computed take-off distance and stability/angle of attack protection." -- re HondaJet Elite -- https://en.m.wikipedia.org/wiki/Honda_HA-420_HondaJet
Related re Embraer Phenom 100 -- https://blogs.mentor.com/jvandomelen/blog/2011/02/09/take-off-and-landing-on-t