A4
Not sure I'm understanding you correctly.
Don't know specifically how Emerg Turns are designed by the 'researchers' but think about it practically.
Your perf calculations tell you what weight you can safely take off given the conditions of the day. Some days that might be MTOW, other days less. QNH, temp etc are all taken into account in these calculations.
If an Emerg Turn is specified it must be followed and is certfied for up to the Max allowed take off weight for the day - no heavier.
So you return following an engine failure - if your take off weight was within the calculated max TOW then your Go around will as well. If you can legitimately take off on a runway within perf requirements then you can go around as well (single engine above v1 etc).
If you haven't got the performance for a go around then you shouldn't have taken off in the first place.
Landing weights is a different issue altogether.
Sorry if I've misunderstood your point.