I was in Turkey in 2010 (let's not talk about that "competition", I think you know why

) and in terms of fans, unfortunately there was VERY LITTLE diversity. Don't get me wrong, organization was excellent, the halls were pretty full and crowd was passionate sometimes. The issue was that with the location of Turkey, the fandom of traditional European power houses was just not there. It has little to do with promotion, it's just a nature of the fact. Regarding Berlin, the halls would be full whenever Germany played, it's another issue that Turks and Serbs would kill for tickets and they filled the hall. It means so much more to them than actually it does Germans. Still Germans would've filed it themselves as well, they have good crowds in club basketball EL/Eurocup. Also the fact that there is a strong diaspora for many nations in Germany and their passion for BB, it is actually a positive for picking Berlin. It makes that much more sense.
Regarding Belgrade, the hosting would be easy because it would be filled with neighbors without problems. Few hours driving you get Croats, Slovenes, Bosnians, Macedonians, Montenegro, Greece and of course a huge domestic crowd which loves basketball and will go to watch Belgium-Georgia as well.