Your argument seems to make sense. Just one note: I worked in game industry since year 2005 as engine programmer and I have experience with different engines including AAA engine (Mafia II game). I must say, this “units restriction” must be some Unreal speciality 
But I don’t want to be negativistic, I can live with centimeters for now…
At the earliest, I must force Physical Asset Tool to accept my aircraft models.