Come on, that would be simple. The solution is even related to the given example of Torx screwdrivers (although those actually serve a purpose instead of just b

Come on, that would be simple. The solution is even related to the given example of Torx screwdrivers (although those actually serve a purpose instead of just being a nuisance): make sure the filament has to have a certain shape, say 'penta-lobe filament', sell the idea as 'improved heat transfer filament' with a 'large surface area ensuring quick melt with lower heat requirements'. Patent the shape - no matter that it represents a trivial 'innovation', defending against patent infringement is expensive - and do some creative advertising.