I think you'd get a lot of public support for this kind of "usage" or "intent"-based restrictions on legal weapon types. It would resonate with a lot of gun owners as well. However, what makes an approach like this pretty thorny to implement is that at some point an agent of the state will need to physically show up at people's doors and demand they turn over the weapons that are no longer legal to possess or be arrested. Obviously there going to be some violent confrontations during these encounters but even worse, this action would completely validate not just the "THEY'RE GOING TO TAKE ALL OUR GUNS!!" viewpoint, but every other reactionary, slippery-slope fear that the folks with this worldview hold. I think it would get really ugly.
I happen to agree very strongly that re-evaluating what weapon types are legal to possess is a helpful discussion to have. The practical limitations around removing existing gun types from the population though may limit implementation to something like banning NEW sales of these restricted types and grandfathering in any weapons already in the wild. This clearly reduces the benefits gained by the change significantly and possibly creates more problems than it solves.
The Gun Deaths In America data presented in this FiveThirtyEight article is important to consider (here's that subtly in discourse again) when discussing the impact of any propsed legislative change. https://fivethirtyeight.com/features/mass-shootings-are-a-bad-way-to-understand-gun-violence/
Is our goal to prevent deaths from guns? What kinds of deaths? Would the proposed legislation have any impact on suicides, domestic violence, or mass shootings only? Are we proposing something as difficult to implement as confiscating guns door-to-door to only impact 1% of gun related deaths?
I liked Seth Meyers recent point about our options: "Congress, are there no steps we can take as a nation to prevent gun violence, or is this just how it is and how it's going to continue to be?"
We forget that in a democracy we can always try to change what we value and how we want our country to operate. It may be incredibly difficult to make certain kinds of changes but there is path forward for almost any change we want to make. We have to decide first what we want to accomplish. Perhaps our nation's answer is actually "This just how it is and how it's going to continue to be." I just don't believe our public discourse is capable of a reasoned, practical, and nuanced evaluation of our options. Not even at the theoretical or conceptual level let alone at the implementation level. It's going to be done in the intellectual vacuum of "all guns should be banned, period" vs. "don't touch any of our guns or ammo, period".