Assuming a type of plane has a technical issue that must be fixed related to its flight behavior, could the plane be derated to add safety margin (instead of banning it).

What I have in mind is having longer runway requirements, lower airport T, higher air pressure, softer rate of climb, lower take off weight, etc. 

Could this work technically? Legally?

This is inspired by the recent crashes of Boeing 737 MAX-8s, but the question is about types in general.