Russia can’t pay the costs of restoration they don’t have the money, any amountof repayment is goingto be a token value to the true cost. We also learned from WWI, that saddling nations with crushing reparations is bad.
Two words: Mining concessions. Even creates jobs for Russians. Other countries then can guarantee loans against future profits from those. That’s going to be very hard for any future Russian government to disagree with if it’s the condition for lifting sanctions because if there’s one thing Russia has then that’s abundant natural resources. Would also do Russia good to not be able to earn that much foreign currency with resource exports for a change, giving an impulse to develop internally.
As to corruption, well, EPPO. There’s already quite extensive working arrangements in place, as it stands I absolutely expect Ukraine to join EPPO (which would mean they can prosecute in Ukraine). It may not be an official requirement to join but that doesn’t mean that it’s not mandatory.