... one of the head scratching inconsistencies in the system ... it presupposes that one can track the centreline for a low vis takeoff until the splay commences .. which can be a bit difficult in older (non FMS) jets with significant deck angles. So far as turns are concerned, it would be very unusual to schedule a turn before runway head.
In practice, a sensible ops engineer will look at this problem and figure out a way to reduce the off centreline tracking risk in the case of a long runway with significant obstacles for a takeoff by a smaller aircraft .... this might well be a matter of generating a more conservative trapezoid from a convenient mid runway position if the case dictates.
Above all, blind compliance with the rules is not always a good thing ... one should consider that the rules give a baseline for commonsense to be applied .. same thing applies for the design standards. That is to say, there are occasions where the rules should be seen to be inadequate for the requirements of reasonable risk management and should be modified conservatively to reduce risk ....