LSM,
I'm afraid your information regarding 175 performance is still incorrect. Given calm conditions on 20 at SOU with a pressure of 1013 the aircraft does not become limited until 28C. Furthermore, RTOM is only restricted by about 150kg at 30C. Obviously, a breath of wind or some high pressure will improve matters. Landing performance is never an issue.
Maybe you didn't use the optimum parameters when doing your calcs. ie T/o 1, ECS OFF, MACTOW >16% ? Or maybe you were using the paper tables?
Given that Flybe limit the MTOM presumably to reduce nav charges, it's not really such a ground-gripper, is it? Obviously, it's also never going to be a long range bucket and spade jet from any airport given the reduced MTOM. Of course, Flybe could choose to increase the MTOM on some of the fleet should they wish to operate some longer routes from longer runways in the future.