Fair enough if we're just talking about Russia vs Ukraine or other small, non-Nato countries.
But "Eastern Europe" is typically considered the former Soviet-bloc countries now part of NATO. Not sure Russia could sustain any kind of footing, war or otherwise, if they poked NATO in the eye.
There isn't even an argument to cede Eastern Europe to avoid a nuclear war. There would be no reason not to utterly crush Russia if they made an attack against Poland, etc. And if we all get nuked, we all get nuked. That's just how it is.
In every conceivable way, allowing Russia to take NATO territory by force is a worse outcome than just letting the nukes fly. I don't think we'd appease them, at all. We'd push them back and they'd either start a nuclear war or fold and surrender.
Obviously it's not a great outcome, but it's inconceivable that we'd just let Russia take back Eastern Europe, and they know it. So they'd have to be completely off their rocker, and no amount of preparedness on their part would prevent an absolutely Armageddon scenario, at least for them (and probably for us too).