That could so easily escalate to nuclear war, I could see that being a downside.
Let's see. Russia has:
1. Made a veiled threat to down the ISS over China, India, US, or Europe
2. Lay down retaliation the likes of which "history has never seen before"
3. Vetoed the UN vote on retracting his forces
4. Invited Belarus, Kazakhstan, and the Chechens to fight
5. Shown he is completely willing to disobey any and all international sanctions, contraventions, and rules of war.
It could go nuclear. I don't think it's out of the realm of possibility for Russia to nuke a smaller nation that intervenes, but invoking the wrath of every NATO nation in total nuclear war would destroy the world. I think Russia controls a lot of oil that the world depends on and has every intention of using that against the West.
Putin is a strategist, to the best of my knowledge, not a reckless idiot. When it comes to nuclear war, you have to ask yourself: does the nation in question really want to vaporize the entire world? Because that's exactly what will happen. Russia is really good at being scary and making threats. I don't think it'll add up to anything. I'm not sure what he would do to show he isn't fucking around, but these threats alone are enough to make NATO think twice before intervening in any meaningful way.