Meaningless. Ukrainians are already expendable, the only thing that is desired by the west is the land and a handful of miserable people to exploit within it. Government buildings? Who cares. The real decisions in the west's opinion will be made at Blackrock HQ. The west doesn't care about Russia responding within the theater of war. Nearly everything there aside from embassies is fair game already for Russia and the west doesn't dispute that being part of a limited war with Ukraine.

What the west has gotten away with is direct involvement in hitting Russia. The tit for tat is not more strikes in Ukraine but strikes against the west that is via their weapons supply, their personnel, their satellites, etc directly striking Russia and merely staging such attacks from a third party's land. Give Ansar Allah powerful anti-ship weapons and anti-air, give them the ability to shoot down US and NATO jets flying over Yemen, give them the ability to maim or sink NATO ships in the area and that will be a tit for tat.

Hitting embassies as someone else mentioned is a different kind of escalation. Embassies are presumed to not only be sovereign soil but above conflicts, even in war one doesn't hit the embassies of one's enemy, you deport their personnel and then you can blow it up after they've had a chance to close down and take out what needs to be taken out. But you don't strike them. The lawless west gets away with doing "oopsies" to the Chinese embassy once because they are the hegemon and they can manufacture the lie that it was an accident whereas Russia doing this to the US embassy, no one would believe it was an accident and it would be used to stir up outrage and indeed the propagandized political class would feel it as an extra affront to them and their special exemption in state departments and diplomatic and spying corps to be above being hit as if they were merely another military target. Whereas they have some distance mentally and emotionally from their troops and militaries the decision-makers very much see things like embassies I believe as a kind of special sacred ground, the defiling of which would likely anger them more than a military strike and do more to convince them they are in a life or death struggle that must be fought to the last if they're not already believing that. But it falls into the west's desires to paint Russia as lawless, as being a rogue state, as not following the rules. Whereas a military strike that's an exact mirror of what the west is now doing with ATACMs is fair play, the west won't see it that way but they're delusional, however the global south will and that optic matters a bit.