The problem in the west is that if you have an Ipad 1 then you are out of date... if the Ipad 1 does everything you need for it to do, then it is not out of date... they are just being stuck up snobs.
It would help with such questions if you give some context, for instance a country in Africa might have a significant supply of T-34s and ZSU-57-2s and so what is their cheapest upgrade options.
Just as an example I would say that a T-34 and ZSU-57-2 are simple basic machines that would be easier to use and upgrade in African conditions that some uber expensive super tank, but the fact that the ZSU-57-2 is T-55 based, but with lightened armour I would say that the T-34s could have their turrets removed and mounted on boats to create cheap gun boats and the vehicles reduced to scrap and money spent buying more T-55s to have automotive commonality.
The 100mm gun of the T-54/55 is rather more effective than the light gun of the T-34, whether it is a 76.2mm or an 85mm.
Many upgrades of the T-55 start by replacing the turret with an early model T-72 turret, so the abundance of the T-72s could make a bulk purchase of such vehicles a much more sensible proposition.
The critical thing would be to enforce the rule that with regards to internal ammo storage only 22 round inside the autoloader and no other main gun ammo as it is a serious fire risk. Perhaps small trailers could be fitted to carry more ammo externally safely.
With T-72s you could develop a separate vehicle with the A-220 turret with a single 57mm gun for ground support and anti aircraft use.