Now I have some figures for you about the known and speculated possible venues:
Vienna: Wiener Stadthalle - 16,000 spectators max., Messe Wien - 15,000
Graz: Davis Cup Center in Unterpremstätten - 38,000 max. (huge!), Stadthalle Graz - 11,000
Oberwart: Burgenlandhalle - 10,000 max.
Wels: Messe Wels - 11,000 max.
Linz: Linzer Hafen - could be big, venue not ready yet
Innsbruck: Olympia World - 14,000
If we allow enough space for a big stage and green room, the air gets thin for some of them since ORF requries room for an audience of at least 10,000; Graz could be a shock winner, but on the other hand, it's the capital city of Tom's home state Styria, and the city where he studied fashion and planned his life...
Graz would also be a friendly choice for the southernly neighbours and Balkan countries.
Unterpremstätten is located at a small lake directly at Graz International Airport.
https://www.google.com/maps/place/U...m2!3m1!1s0x476fb5e324f6e2e7:0x9f1c35b66838383
What I'd miss about Graz, is the typical Austrian Alpine feeling (no mountains) or classical sound of music feeling (like Salzburg, Vienna). It's strange, but beautiful, mostly sunny and warm, very friendly.... has a flair of Southern Europe already.... Graz can't really sell clichés.....
I don't think Klagenfurt with their big stadium can pull it off due to political reasons and recent scandals.