I think Russia is already mad enough at Ukriane when they started ciphoning the gas line. Ukraine is already an avowed competitor of Russia and they won't let much of anything stand in their way to fight for that market. My question wasn't Ukraine but what India would do if Russia sold Pak tanks. Would India cancel their cooperation agreement?
In my view there is only a very small chance of this happening because of the totality of the Indian relationship.
It seems to me that you are still colouring your opinions based on the Cold War. The Ukranians are trying to resist big bad Russia, therefore its tanks must be better.
While no doubt there is talent and expereince in Ukraine for producing all sorts of weapon systems, the complexity of transition to market economy and participating in the defence market is daunting for aall FSU states.
Procurement decisions as you pointed out are not so simple, and in case of India they are complex not just because of the individual platforms involved, but the greater economic and political issues. Russia is supplying India's WHOLE STRUCTURE defence forces. Besides that BOTH need to consider long term strategic implications of developments in the Islamic world and China. Neither Ukraine, nor Belarus have these considerations, so their 'marketing' is more based on immediate needs. My analysis is based on this POV.
Can China become Pakistan's 'Russia' with Ukranian help? Aside from the Ukranian desire to integrate into EU (and NATO), I see this as a temporary 'need' for China, and an equally temporary 'want' for Pakistan. I could be wrong of course.