How?
Like, how can we actually protect the facility without actually hurting him? Your plan doesn't actually solve that problem either. Since he's utterly content to ignore us unless we hit him at least twice in a given round, and your plan doesn't do that either.
And we don't have an option of just getting in the way either, I explicitly tried to herd it with our round one options, and it did fuck-all, it's perfectly content to go around us if we're not doing enough damage--which is exactly what happened. We don't have the mobility to catch it, and even when we did, we didn't have the ability to herd it at all, because it's just too singleminded--it was explicitly called out as being a thing, that it was content to ignore us and go around us if we weren't doing enough damage at any given moment, and that was when its mobility was considerably less than it is right now.
Our only recourse really is to try and called shot its mobility down and then try to kill it before it can get it back, which is precisely what my plan tries to do. To try and Called Shot its Evasion down with every reroll and every action we can muster, and then lay down so much damage before it gets it back that it dies, and we are very good at that. If we can successfully immobilize it for even one round? It's slated to take up to 22 damage before it can get back up. Enough to completely kill it, and that assumes the Called Shot to immobilize it for a round does zero damage somehow if it hits.
Yes, if this fails, we're screwed--but that's a risk even with your plan, because you try to do the exact same thing, just that you're assuming that somehow we'll be allowed to tank it when we have nothing to actually force it to fight us, since it can just go around us.
(Though that's cause for a new tech. Some kind of grapple launcher to force it to fight us instead of get wandering eyes?)