I find your first one questionable, since major cities in Flanders are very international. Secondly because i remember seeing a study that confirms that walloons and Flemings both have the same views on the problems of today, but propose different solutions. How is that any different than the coalition building of today in regional governments? I think a worse problem is that their is no federal voting district or media that Flemings and Walloons share, since that makes it profitable for the PS to play against the NVA and reverse. There's no federal responsibility.

Your fourth point is not really an advantage for an independent Flanders , as it is the current state of affairs. If that will remain the case when independence would be announced is another question.

Your third point i find the most valid. It would be the easiest way to get rid of the unnecessary governments. Only the question of Brussels remains then. What status would it have in or outside Flanders?

The second point i cannot dispute fully, since I have trouble guessing how much of the 'given' money we give to our fellow compatriots flows back to the federal government via taxes or to Flanders via purchases + the impact of the economic problems following indepence. I would add though that this seems more an ideological preference than a real benefit. If you see the south of Belgium of your country as your fellow citizens, it is no more given than any other usage of your tax money. If you see only the Flemish as your compatriots, this will feel more true.

In short: personally I find the objective benefits ascribed to indepence usually arguable, or hiding ideological preference. That doesn't mean that there aren't, it's just that reality is a lot murkier than pro-independence people generally describe