Just a thought exercise.
It seems that there are no any force or organisation who clearly want and can storm Capitol in closest future. I guess everything that could happen from the right side have been already happened in the form of large peaceful meeting in Washington DC. Even a hundred of Capitol visitors did absolutely nothing to assume a real threat of that scale. Lefts seem to be indifferent too.
So, there are no obvious reasons for such extreme measures. Let's tinhk, what event could result in a serious and wide assault of some place? It have to be something nearly religious and outstanding. And it should be something, that authorities and MSM could not prevent at all. It is definitely not some political or social things, I think even if authorities repel the whole constitution, it will not cause so massive assault authorities prepared for. The covid bullshit show it clearly.
I could imagine only something like an official aliens arrival and meeting with authorities. Only that kind of event will need this level of measures, because an unlimited mixed crowd, full of religious fanatics and unstable individuals will immidiately rush to worship (or to fight) the "miracle" in absolutely insane and completely uncontrolled manner.
In no case I want to judge or interfere internal US politics, but I can't keep myself from posting this crazy idea. Sorry if it hurts your feelings. :)
You don't need to build walls around Capitol to confiscate guns. You need just boring paperworks and silent local laws, something like "you know, that domestic terrorists, we don't want to take your gun, but you are in 10 mile radius from government building, please store your gun at police dept, or move to other location temporary, it's just for few weeks, nothing to worry about".