In my company we use derate and assumed thrust method. The other day we took of with 22k and mid 30 degrees
on the assumed temp. Result was 81% N1 and flaps 1. It is possible and you have to follow your SOP's very closely not to screw up. There have been lots of accidents and incidents entering data from the EFB into the FMC.
But I never heard someone entering the TOC temperature on the N1 limit page as OAT.
Training standards and SMS system should be reviewed in this company.