The idea of suing the West for reparations is interesting...or maybe i should say amusing, because i doubt it will go anywhere with how much control the West has over international courts. And best case scenario, say they win, the US can always just refuse to pay. I mean can you see Trump ever paying Ukraine or any other country reparations if an international court orders him to? Never in a million years. And frankly i think the same goes for any US administration. They'd rather just pull out of any organizations or treaties that they've signed that would try to make them do something like that.

No, i think the simpler solution is for Ukraine to just default on their debt. In fact not even call it a default but simply declare that they just don't recognize that debt - as far as the new government is concerned it never existed since it was taken on by an illegitimate regime. What's the worst the West can do? Sanction them? The worst sanctions the West could impose would still be better than the only other alternative which is privatize and sell off literally everything and let the IMF run your country (which is what will happen if any kind of western controlled government remains in charge).