I don't have a lot to say about the functionality or specifications here, but I feel like there's a new conceptual issue raised by non-lethal, or notionally non-lethal weapons.
Constitutional arguments are about the right to self-defense. That's not necessarily the same as killing someone, and you don't necessarily have a right to killing in and of itself, but only as a means to an end for self-defense. I suppose it depends on what flavor of defense of the second amendment you favor, but it seems like self-defense can be associated with incapacitation, need not necessarily depend on the capability of killing.
If that's true, access to weapons for the purpose of self-defense that aren't capable of killing would seem to open up a lot of possibilities for regulating traditional firearms. If (I said if!) there are equally effective alternatives for the purpose of self-defense, then that constitutional right can be satisfied without the need for traditional firearms that are capable of killing.
Insofar as they can replace traditional firearms, I find that promising, but obviously this brings a fair amount of unintended complexity; for instance non-lethal self defense may open up entirely new dimensions of cruel maiming and non-lethal suffering, it's may create complexities relating to whether something's actually non-lethal, it may have an effect of increasing the sum total of use of force by introducing non-lethal force into lower and lower stakes situations leading to a net increase of physical coercion, and there may be cultural resistance to the idea ever becoming mainstream because it would be too reformist and therefore liberal.
I think these all have to be navigated, but I think the trade-off is worth considering. I also think that strong gun regulation is worth considering, and personally just don't endorse wide distribution of guns in any form whatsoever, so I consider this a workaround peculiar to the culture of America.