All far to complicated
For a Flex (Airbus)/Assumed (everybody else) temp takeoff VMCG is based on TOGA (Max) thrust. You can therefore safely use TOGA if need be.
For a Derate takeoff the VMCG is based on the lower engine thrust. Using TOGA at speeds close to V1 might result in loss of directional control.
For most modern airliners, a derate takeoff will only be beneficial on contaminated runways where the lower thrust VMCG is an advantage.