Well, one has to remember, that a procedure design, has to take into account all of the worst case factors...
MLW, max bleeds, dirty engine, low end of the CAT approach speed, initiation of missed, pilot/aircraft reaction time...and especially temperature/met conditions.
FlightPath...
Procedure design has nothing to do with how an airplane is flown. As I mentioned in my earlier post, it doesn't matter if the plane is being flown on 1 engine or 8 engines, as long as it can maintain the minimum climb gradient and carries out the proper rate one turns and maintains the airplane within the allocated distances associated with the category, the airplane will be safe!
One quick point before moving on: categories (A, B, C, D, E) are based on indicated airspeeds. You are supposed to fly according to the minima associated with the category in which you're flying the maneuver at. For example: if you're flying a circling procedure at 140 KIAS then you're supposed to adhere to Cat C minima and the circling distance of 1.7NM. But, I think it should be understood that it does not matter what airspeed you fly your maneuver at, if you maintain within the limits prescribed for that category, you will be safe. If you fly 300 KIAS while circling and keep it within 1.3NM then you could go to category A minima and be safe. If you're flying at 140 KIAS while circling but would like some extra room to maneuver, you may go to the category D minima and keep it within 2.3NM instead of the 1.7NM for category C.
I think it needs to be remembered that there is a HUGE difference between
procedure design and
airplane performance.
As for the determination of procedure design, there are certain factors for wind and imperfect turning that is applied to the flight path to ensure protection up to a certain limit. The worst case is not the low end of the category approach speed, it is the high end. If you're at the high end you will require a greater turning radius thus requiring larger protection limits while maneuvering. I agree that they they add a fudge factor for pilot/aircraft reaction time, and temperature/met conditions such as wind - however, I don't agree any consideration is taken for MLW, max bleeds, dirty engine, etc. Those are all specific airplane performance factors.