... and to Hungarians, Russians, Romanians.
I would tend to agree with you, but not entirely.
We Slavs, if serious, for example serious as Jews are, can`t disregard fact about term such is `our ancient Slavic (ie Sarmatian) land`. So, essentially, we talk about Slavic land, in which case, Hungary and Romania don`t have to be asked about anything in the region. As a Serbian, I have every respect for Hungarians and Romanians, but, those are facts.
See, what we know for certainty is that what is now Ukraine and Crimea, represent lands that belong to Slavs (ie Sarmatians) since time immemorial. In other words, if for any reason, Slavs on those lands can`t live together, they do have right to separate along ethnic lines (or call it tribal lines). Some with bigger rights- those who are natives and some with lesser rights- those who have only historical rights. In this case, most probably that we can`t say that all Slavs there have rights as natives and as historical entities. Most probably that only Serbians there deserved some historical rights (established their own historical provinces escaping from Balkan during Ottoman invasion). I`m not sure are Poles (Polani) represent native Slavic tribe of the region (feel free to correct me if I`m wrong), to say that way, or they same as Serbians acquired certain historical rights in the region, in some other circumstances.
So, in situation when ethnic Ukrainians forming their own ethnic state for the first time in their history, they have every right to do so. But, they must consult about borders with other native Slavs in the region. First, with Ruthenians and then with Russians, too. Then comes the talks with Poles and Serbians, who have historical rights, how to compensate them, if there are demands. In my opinion Poles could be compensated by some territory and Serbians, considering obvious geographical reasons could be satisfied with some constitutional mention of their rights in Ukraine- rights on cultural autonomy, preferable status of their business in their ethnic regions, etc, etc, possibilities.
All others, non-Slavs, who have some demands, aren`t in situation to pressuring. If successors (after land is divided, new borders established) of what is now Ukraine can afford to do that, they should compensate Hungary and Romania, if those countries deserve that, by some other means, without being obliged to give territory.
In my opinion, neither Hungary, neither Romania deserve historical rights to claim anything. Why? As nations, Hungarians and Romanians were by force of invaders formed on native Slavic ground even if we speak about territory of Hungary and Romania. Still, what they from Slavs deserved with time, is level of some respect and they should get it.