This deal is doomed to fail, there is no way 'coalition of willing' troops will be able to stay in Ukraine for a sustained period, with right wing politics taking over the western world it will only be a matter of time before we 'need to bring the troops home' rhetoric happens, and it will probably allow the likes of reform to gain more ground campaigning on this.
Secondly and more importantly there is no way Russia will agree to a deal with European troops on their doorstep, even Trump understands this.
I’ll respectfully disagree, only because we don’t have all the details and facts, we’re just speculating here and also because I’m desperately clinging to some sort of hope or optimism.
1) Even you take Trump and the U.S. out of the equation for a second it was always going to be a non-starter for:
1) Full NATO membership for Ukraine
2) There almost certainly won’t be any NATO/UN or Euro troops on the frontline. A ceasefire would have to happen and hold and any non-Ukrainian troops would be well away from the front lines. Also there would likely have to be demilitarized zone established between the front lines.
3) The reasonable security guarantees Ukraine could hope for would be a no-fly zone / missile defenses established (whether Ukrainian based or in Poland for example) and Euro troops around like Kyiv/Lviv - deterrent for launching missiles at major cities and or a backstop if Russia blitzed across the frontline and went for the jugular again.
2) We have no idea what Putin actually wants at this point. If you look at ISW projections it’s probably 2 more years of fighting to take Donetsk and the provinces they have significant footing in completely and at a high price at that.
3) We really have no idea what a post-Putin regime will look like as well, and very little indications of what, if any, pressure Putin is under to end the war. Russia, post-Putin may not be as invested in trying to take it over again.
4) Ukraine is almost certainly going to have to concede territory.
So a non-US backed ceasefire could potentially work. Even if you have a no fly zone based on deterrence from air defenses and jet fighters based in existing NATO - Poland and Hungary(I know, I know) for example and smaller deterrent ground forces away from the front. For these reasons:
1) intelligence would show a massive buildup for a second inavasion
2) skirmishes across the demilitarized zone would have to managed
3) incursions, especially a major incursion, across the demilitarized zone could involve UK/French and Euro air power directly engaging Russian air forces in combat. That’s about as good as you can get without being a member of NATO for Ukraine.
Russia, also gets some territory. Putin looks like a winner - and there’s nothing to stop them from hybrid warfare trying to influence elections, etc in Ukraine. It will probably take a generation of Ukrainians to forget animosity towards Russia, but they can try. Also, hybrid warfare is a 2-way street. The territory conceded has to be held, either through brute force or hearts and minds. Tough ask for the Russkies. They might have to invest in counter-insurgency for a generation.
It really boils down to, what does Putin want at this point? Is he satisfied with what he’s taken or does he want more? Even if Trump totally walks away, and Europe folds completely, it will be still be damn expensive and costly to take the rest of Ukraine in one piece, much less occupy it and hold it. It’ll make Afghanistan look like a cake-walk.