I think what we are being asked about is "assumed temperature" method of calculating take off performance.
In your sample if the data supports a 43 degree day assummed temp and the power is set for this condition the takeoff will be very close to a 43 degree day takeoff.
Now you confuss me a bit. If the runway condition is poor and the Captain want to spend less time on the runway reducing the assummed temperature will reduce the take off roll. The trust would be set for this new assumed temperature.
The advantages of using assumed temperature,
- less likely to experience and engine failure, because of placeing less demand on the engine. (less rpm and turbine temperature, longer engine life, better economics..)
- if the engine fails, before or after V1, it is an easier aircraft to control, less rudder or wing into the failed engine, I like this reason best!
Remember assumed temperature still gives the crew all the perfomance to stop or continue at that critical before/after V1. Some companies will even add an additional margin. The other common factor is fixing the assumed temperature limit, by either a fixed degree, say 48C or a maximum of 25 degrees over actual temperature.
Safety is paramount and this method increase both safety and operating efficiencies.
Hope I helped,