Agreed. And I would toss in a fully reliable end product, if done correctly....it will have to be something cost effective and relatively practical for the 'end user' to make/create.
Heck I considered an 80% kit a couple years ago as a fun project - and I had the opportunity to buy the remaining parts from a G-17 from a guy who destroyed his frame, but that got bypassed for other things.
My point is while the 80% concept was a practical and easily 'doable' undertaking I wouldn't ever consider something like a liquid polymer & mold tray scenario.
As a fun project, it is a "go", but would never consider it if was highly complicated, required specialized tools, an unreasonable start up cost or the end product would be less than fully reliable.
Things like the GG3 or 3D printing, at it's current level of sophistication, really hold no appeal to me. Start up costs are too high, the GG3 type 0%'s kills a lot of the "fun factor" when all you are doing is pushing a button and the machine does all the work, and 3D printing... the same... but also a highly unreliable/durable end product.
The new rule will certainly cramp a lot of folks style for the forseeable future, but I know people are incredibly clever these days and don't think we've seen the end of "easily" and "readily" legal products yet. Whatever the new form takes though, I dunno, and may be some lag time before whatever form it takes to really mature into a reliable product... but no doubt there will be alternatives somewhere down the pike.