I've read up on this and learned that you can get a high temp extruder with a heated bed to print with nylon filament, still not as strong as molded plastic because you can't add reinforced fibers... but you can theoretically produce parts on par with Traxxas/Tamiya quality, just not RPM quality.

The hotter temp extruders need a larger nozzle to prevent clogging and this also forces you to lose precision for fancy curves so chances are you'll need to do additional milling of the parts to file any rounded edges, ream holes, etc... making it more impractical.

I've come to the conclusion that it would be better to use a CNC to mill custom molds and then you can experiment with custom fiber reinforced blends using a mold injector to make your own parts. You can still use a 3D printer for prototyping, then once you have a design that works, you simply perform an inverse tooling path on the CNC to mill the molds + injection hole.