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 biodegradable filament like PLA that can be printed cheaply and easily with little know-how that decomposes fully.

What are the ideal requirements and how might they be implemented?

• Printable: Fuse deposition modeling (FDM)-printed: 2-piece (or more) interlocking design capable of being produced on cheap commodity printers with small (sub-200mm) beds.
  
  The dirt-cheap $100 printers out there ought to be able to knock these out. For an investment of $20 or so in filament, anyone could print a few pairs of frames.
  
  What's so great about printing versus something like CNC? Why not just machine from UHMW and call it a day? FDM printing involves just one production operation that's almost fully automated by layer slicing software.
• Durable: Designed with wider minimum thicknesses, particularly in high stress areas, such as UFS mounting points and wheel axle holes where FDM-printed engineering samples typically fail. This may result in a slightly odd-looking finished piece aesthetic, and prints will obviously need to be run at or near 100% infill. The fill pattern may end up being particularly important. There might also be a realistic weight limit per ride configuration: say, 180lbs distributed across a four-wheeled flat setup, or 150lbs for a freestyle set with only 2 wheels shouldering the weight.
  3-month/20-hour use or better lifetime desirable. Print delamination, cracking and failure will occur but should happen gracefully: correctable in a predictable manner like a bald auto tire leaking air swapped prior to a roadtrip.
  Additional strength to be added with post-print sub-boil water annealing, which anyone with fire, water and a pot can perform.
  Another, less preferable, less accessible and complexity-adding approach would be to source a biodegradable resin and fill strategically hollow prints.
• Compostable: Printable using PLA filament (polylactic acid), which is made from corn/beet/sugarcane/etc. and is fully compostable.
  Member that Roaches pitch about the "first" "partially" most "green" skate ever? Yeah, that's just a little PLA and PCR material swirled around with some marketing juice: no composting there bro.

The same principles could be applied to pretty much any soul plate with considerably less difficulty.

In case you're wondering: 100% pure PLA's clacky, but it slides great. Especially when its surface friction coefficient is compared to a fiberglass-filled nylon plastic (like Zytel) currently in widespread use for virtually all injection molded frames and soul plates.0

Design experiments to follow.

• You trust a NASA PowerPoint presentation in PDF format, right? Compare page 20 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160010284.pdf to page 3 https://www.dupont.com/content/dam/dupont/amer/us/en/transportation-industrial/public/documents/en/Brochure_DuPont_Performance_Materials_Healthcare_Brochure_A11217_020617-FINAL.pdf. Printed PLA is probably gonna slide a little or a lot better than printed or molded Zytel. ↑