Ukraine is an unlikely customer due to:
•The US involvement in Kiev's decision-making process.
•Russia would almost immediately object such an attempt due to the nature of their relationship with China in the long run.
•Ukraine seriously lacks the economic power to proceed with such procurement. Preferring second-hand western aircrafts would do them more good considering roughly 2/3 of the country is in range of Russian air defence systems.
Sorry for sailing off the topic for a moment. My point is that potential customers for J-10, are either poor or lies within the Russian sphere of influence. And I don't actually believe Chinese actually try to market this aircraft. They're more invested in JF-17 story, IMO.
Yeah it is highly unlikely China would supply the fighters. Especially considering Ukraine plans to join NATO eventually.
What is more likely, I think, is that they would get F-16s like other Eastern European countries have done.
The fact is there are many F-16s flooding the market right now. Even more once available F-16s start being replaced en masse with the F-35.
I think Iraq or Iran might make more sense. But Iraq already has F-16 fighters. While Iran, I don't know what to think about their purchases but they don't seem to purchase a lot of weapon systems from China as is.