You seem to forget that not only Paraguay but all Alto Peru (Bolivia) and parts of Peru, are part of the UP. Without mention that the OTL 'Dessert campaign' was butterflied, so ITTL incorporation and colonization of the Patagonia to the UP, would be done in a radically different way to OTL... Also, you seem to assume, very little or null internal emigration and/or that the minorities or the Natives/Amerindians, would all of them stay in their own regions. When, I think that would be larger than OTL, either rural (seeking new lands) or urban emigration and that it would affect the UP demography and, of course electoral policies...
1) From what we've seen the opnmes where they had the most power was Paraguay. Bolivia was still pretty "colonial" just like the rest of the UP even if their antives are treated much better if only by virtue of how big of a chunk of their demographics they are.
2) I used Paraguay as an example (eg),
you know.
3) What does migration have to do with anything? People would still care first and foremost about those of their own ethnic make up. This was the case all over history and was pretty much the case in the americas too. There aren't going to be laws fucking over an specific ethnicity but entire communities will be fucked over. So you could have, say Tobas living in Santa Cruz (or however it was called ITTL, I forgot) in some settler city while some local community is pushed out by the settler homesteads or big landholder (mostly through abuse of the law though I wouldn't be surprised if violence played a part). We often saw "white" minorities similarly abused in Europe's multi-ethnic empires in the same way, why would it suddenly be different here?
4) You fall into the incredibly boring tendency of ATL writers of making everything better. No one wants to read a wankfest where one country somehow pushes ahead of everyone else and reaches 21st century enlightened morals while their economy magically competes with the worlds powers. The UP is still a racist (by our standards) settler country who believes a bunch of crap that was common in the era. That they (settlers and settler descended inhabitants) somehow managed to learn how to (mostly) live in peace with a big chunk of the people their ancestors crushed under their irone soled boots and that said people also integrated fairly well into what came out doesn't change any of this.
Anyway, I know we don't see eye to eye in this matter but I just ask yoiu to look at your proposals and think "Would it be fun to read about (or realistic) if it was another country?" Would you read a TL where the US became enlightened and suddenly racism was no more, the blacks were freed and the natives peacefully integrated? With
no buildup on the matter? Because here we had the bases to why thee UP wasn't as virulently racist and settler-style as OTL but not for the level of "equality" you seem to believe we'd see.
I liked how the UP only realistically offered so much. Even if they are shaping up to be US lite there is only so much an unready (because seriously, no one was) military can only offer so much to the mother of all wars happening thousands of kms from their hom turf. Nevertheless, I'm pretty sure their mountain regiments will probably get to become one of their specialities, or at least the ones that are best known outside the country.
My only "problem" (and I use airquotes because I get why it was done that way and don't really disagree) is that the War in Europe is too much the same, the same members, the same results, the same tactics and strategic moves ,etc. I get that planning a completely alternate Great War may not be feasible but I would have hoped for at least some more differences.