are we really going to need full rated thrust with an engine failure at low weight, leading to controllability issues
No, hence the initial suggestion for fixed derated thrust and additional assumed temperature method to be used. Once a continuous climb clearance has or can be attained, after cutback (1500' AGL default but overridable), select full thrust.
This reduces impact of any failure on departure, such as a bird strike or engine failure, while minimising time to cruise level afterwards and thus saving fuel.