The main problem thus far (2020) with printable parts is a lack of durability. This isn't an issue for grind blocks or antirockers, which can be trivially reprinted- but an item like a complete plastic frame requires a more expensive printing technique like SLS than good 'ole FDM, or less environmentally friendly filaments (think fancy fiber-nylon) to last very long -- and SLS prints are probably going to be produced by a third party with deep pockets.

But it might be possible to overcome this hurdle by designing parts specifically for FDM, meanwhile leveraging the positive side effects of a ...