the aircraft needs an advanced throttle setting for the same TO/GO thrust at the actual OAT
I think that the point of the exercise is being overlooked
(a) depending on circumstances, a full thrust takeoff may not be "necessary" .. ie at full (not necessarily rated) thrust the aircraft uses less than the available distances, climbs at a gradient greater than the minimum required, etc.
(b) in such circumstances, if one were to conduct the takeoff at a somewhat lesser thrust, these conservative margins might be reduced toward (or become coincident with) the minimum required performance.
(c) the assumed temperature approach is a simple way to adjust the thrust downwards. If today the OAT is 20 deg but the RTOW chart indicates that, at the actual weight, the takeoff can be conducted at, say 40 deg, then to set the thrust to a level appropriate to 40 deg will be adequate. It will also be conservative as the actual OAT is less than that assumed for the calculation.
ie there is no intent to operate at full thrust .. the intent is to operate as some lesser thrust .. the benefits being related to engine costs.
you are more restricted in terms of runways conditions brake anti-skip... than when you use Derate
May we have some specific examples ? the question confuses me a little.