I doubt NATO gonna send their best tank, Leopard 2A6-7 or M1A2.
Imagine how it gonna look if those tank getting knock out by Russian ATGM or bog down in muddy terrain. And honestly, see the way Ukraine used these tank, it's not unrealistic to think they gonna get destroyed in a few days after deployed. Western MIC will not happy with that.
And while all these NATO supporter cheering and talking about battle proven of these tank. In reality, they were never deployed in neer peer battle. The closest thing to that was Desert Storm and that was a turkey shoot with full controlled air space.
It's not even just a face thing.
Looking at their latest support for Ukraine, it's clear that they're increasingly going for palliative doses rather than curative doses, so to say.
Trickling in single numbers of HIMARS, Patriot, still forcing Ukraine to rely on jury rigged pickup truck GRAD. 100 humvees and what will likely be the oldest Bradleys found in the storages, at numbers as small as 50.
NATO itself probably knows that this is a trap, a tarpit designed to waste and blunt their offensive force. They're countering it by sending their least desirable stuff.
If they wanted to win, they'd ready up real mechanized formations from outside Ukraine borders and then send them in all at one go. 800+ IFVs of modern type and not relics like M113, 300+ modern tanks, 100+ wheeled MLRS, 50+ tracked MLRS and enough air defense to keep the formation intact.
But that would mean actually pushing into where there are heavy Russian lines. And Russia is beckoning to NATO with their slow advance to come and try it. So far, NATO is having none of that.
Also it is not true that leopard 2A4 and m1a1 were only battle tested against what is practically afk forces in Iraq. They were also battle tested during the Syria war against ISIS. Granted, this wasn't anywhere peer conflict, but at least ISIS had tactics of staying mobile and supporting their infantry.