One of the things that can be a lot of fun in writing future histories is to have an event, a country, or a people that do something that's a little hard to imagine now. Obviously, if you have too many such things, you lose that certain verisimilitude that people read future histories for (nevermind that such events can pretty much be guaranteed to occur and occur quite often - which is why projected future histories written in the past seem laughably quaint at best to utterly mystifying to the modern reader at worst).
I think the biggest example of this particular trend in 2300 (not 2320) is the Confederation of Palestine. It's hard to imagine the scenario described within 2300 today, but such twists of history would be pretty normal in 300 years.
An interesting excercise for board members might not be to deny Austrovenia's existence, but perhaps consider how such a thing would have occurred. It's obviously easier to do than the Confederation of Palestine (as there is a certain amount of historical precedent to an "Austrovenia").
My theory on Austrovenia is that it came about, again, during the dark days shortly after the Twilight War. The two areas have enjoyed historically decent relations, and perhaps with the collapse of the war, the Slovenes didn't feel safe with their Slavic neighbors (who regarded them as "un-Slavic") and instead grew close to Austria to pool resources to rebuild and fend off marauders and so on. As time went on, what was at first a loose association became an alliance, a Federation, and finally a single nation.