History is replete with "should haves" and "would haves." They make interesting debating points for historians. Whatever should have or could have happened with respect to Minsk did not. We are left with what did.
My problem with a notion of anticipating reasonable behavior and dialogue with respect to the ambitions of Putin's Russia is that Ukraine has been an independent nation for thirty years. I would suggest our ability to force Ukraine to simply surrender 25% of its territory to appease Russia would have been misguided at best at any point in those thirty years. That would seem particularly true with respect to the rest of Putin's ambitions to restore a Russian Empire.
Those "reasonable" solutions also completely ignore the results of the 1991 independence referendum in which 84+% of the population took part and 92+% voted in favor of independence. In spite of the majority of the population speaking Russian, fully 83% of the voters of Luhansk and Donetsk voted for independence from Russia. In Zaporizhia and Kherson, recently "annexed" by Russia, the totals were 90%.
So, why should Ukraine not have moved troops into the Donbas in 2014? Ukraine was facing a separatist conflict sponsored by Russia which the vast majority of the people in the region did not support. Under those conditions, who in Ukraine could possibly have agreed to simply surrendering that area and population to Russia regardless of what sort of mini-Marshal plan might have been provided the rest of the country - a proposal that was never on the table.
I think even the most ardent Russian apologists would also be forced to agree that the Ukrainian people have demonstrated overwhelmingly they want to see their future aligned with the EU rather than Moscow. That is a referendum they have courageously voted in every single day since February of 2022.
I see no evidence that an independent Luhansk and Donetsk were ever really a Russian objective. Certainly Russia's actions in September of 22 demonstrated the underlying reality of that ploy.
You have lost me completely with the notion that allowing Russia to take by force 20% of Ukraine is going to somehow usher in this new "split" between Russia and China or form the foundation of a new age of cooperation with Western Europe and the United States. I see no evidence that such an act of appeasement would do anything but embolden Russian ambitions and further solidify its partnership with China.
That said, and thanks to US fecklessness, it is ever more likely that the negotiations that end this war will entertain just such a solution in the Donbas and perhaps much of Zaporizhia and Kherson as well. We will likely get an opportunity to test your theory that Russian victory will usher in a new age of good will and cooperation. I personally think the opposite is far more likely.
