This seems tricky to legislate though. How do regulators decide which parts are like this? How do you deal with "generic parts" holding back innovation in cases where someone has invented an improved version of that part but it's not available as a generic part yet?
Just create a bunch more of those standards, e.g. for batteries, legislate their use, done. As a side effect, products become cheaper because parts will then be available off-the-shelf at economy-of-scale prices, and supply problems also become less likely because there will be numerous vendors for each part.
However, there will be two problems: some things, like cases and special moldings are hard to standardize. So I would suggest legislating that 3D-printing instructions (STL, material, finishing steps) be made available as soon as the part itself is unavailable or too expensive. And very innovative parts should be exempt for the first few years, provided they are measurably and provably better than the standardized equivalents and that a new standard is being created from them.
Looking at my iFixit screwdriver bit set for electronics, which sports some 60+ bits and still doesn't cover everything I happen upon, I'm thinking the standards are being less than helpful here. I mean, it's good to have them, but it would be better to have way fewer equivalent options.