T-80 gas turbine engine would be the go to tank if any. When I travelled the Pamir highway, our diesel 4x4 struggled with the altitude/lack of air, and guy had a petrol 4x4 which was slightly better but still struggled, at one point we went off the main highway and went over a higher pass and you could have walked faster than the 4x4. At around 15,000-16,000ft. I read that an exercise China did was held at around 4,000m (13,000ft roughly). Your right most aircraft and artillery/rockets would be mostly used. Armour would most likely be used in defensive methods, protecting important passes, and overlooking choke points.
To be fair the reason they don't work well at altitude is because the air is different at those altitudes and those engines are designed to be operated at altitudes closer to sea level.
If you have vehicles that are intended to operate in such regions at such altitudes you should be able to modify them to run just fine.
More importantly it would give you a huge advantage to have armour in an environment where the enemy does not have armour.
This is a critical factor that many ignore when they look at light and amphibious or airborne vehicles... they have compromises in their design... normally massively reduced armour to reduce weight, but what they miss is that they bring massive fire power to places where the other side does not have it.
Personally I would think a nice light wheeled 120mm gun/mortar based vehicle would be rather interesting in the mountains... it sounds like the Russians are working on a new family of longer ranged artillery rounds for all of their calibres and a weapon that can fire shells and mortar bombs would be rather useful for direct fire as well as lobbing rounds over ridges into places out of direct line of sight... drones will be useful and of course a few suicide drones would be handy too but gun tube artillery is cheap and efficient.
Indian Army's T 72 with a mine trawl at 15,000ft in Ladakh
Looks like it is coping just fine with the altitude...
It is in Russia's interest to break Pakistan, India, Saudi Arabia, Iran and Turkey into a number of smaller nations. These smaller countries will continuously be fighting against each other and so the US will not be able to use them against Russia.
Interesting that your view match those of America... break all other countries into tiny factions that fight all the time because that will keep them all weak and poor and therefore no threat to us so we can continue to get richer and dominate the entire world.
Creating hell on earth is no future for anyone... not even the US even if they don't understand right now.
Russia can create powerful allies and improve the lives of billions of people simply by working and trading normally with other countries. Not trying to rip them off or steal everything from them or create deals where Russia makes billions and the country Russia is trading with makes nothing.
That is the white colonial European way and it has kept the third world poor and weak which is exactly how they want it.
The whole idea of BRICS is to be human, to accept difference, and to pay a fair price and make a reasonable profit on transactions and deals so the other party makes a reasonable profit too. And I don't mean we are rich France and you are poor african country so we pay a euro for this and we can sell it at home for 10,000 Euros and live like kings... in your economy one Euro is good money.
The west is so evil even rich people decided western countries were screwing the third world too hard and demanded the option of ethical coffee to make them feel better about things.
BRICS is ethical everything, and not imposing western culture, religion, or ethics on other countries. That is why BRICS is going to have most countries wanting to join eventually because it is a free trade group that works by helping other countries and your own country to develop and get better and improve the lives of billions of people instead of the 10,000 odd super rich in the west get slightly richer.