I think the prestige and income issue is going to make a lot of these ideas unlikely. Though, 20/20 hindsight says Bavaria (NOTE: pre-Napoleonic Bavaria is a lot smaller than modern day Bavaria) is better than parts of Italy. During the time periods in questions Bavaria was significantly inferior both revenue wise and prestige wise to even the Duchy of Milan.
Joseph II swap was for part of Austrian Netherlands for the whole of Bavaria, which is why it fell apart. The Austrian Netherlands though a pain, was a rich tax producing pain. So, you do not give your whole cash cow for Bavaria.
To be honest the swap of parts of Italy for Bavaria seems to make more sense in a draw or defeat than an Austrian victory. Maybe something like this:
Polish Succession Austria keeps the Kingdom of Naples but still loses Sicily to Spain like OTL. All else like OTL.
Austrian succession, Austria should do a bit better cause they would be richer the OTL, Naples generates a good chunk of taxes. However, keeping Naples defended would be tough, best case they would lose it then re-take before war end. Next, just like OTL Austria will demand Bavaria which they controlled most of the war. This time though, they can say they will give the Wittlesbach Naples (i.e. making them a King), which Austria figured out is too hard to defend and not worth it (at least in the Austrian Netherlands case you know it forces England to go to war for you). This would put a lot of stress on the Bourbon side as Spain would want Naples, but France is allied to the Wittlesbach. At the same time Prussia would not want Austria getting Bavaria cause it would slightly offset the loss of Silesia within the HRE. England would probably be for the swap as they most likely needed to provide naval aid to Austria to take it back during the war.
Joseph II swap was for part of Austrian Netherlands for the whole of Bavaria, which is why it fell apart. The Austrian Netherlands though a pain, was a rich tax producing pain. So, you do not give your whole cash cow for Bavaria.
To be honest the swap of parts of Italy for Bavaria seems to make more sense in a draw or defeat than an Austrian victory. Maybe something like this:
Polish Succession Austria keeps the Kingdom of Naples but still loses Sicily to Spain like OTL. All else like OTL.
Austrian succession, Austria should do a bit better cause they would be richer the OTL, Naples generates a good chunk of taxes. However, keeping Naples defended would be tough, best case they would lose it then re-take before war end. Next, just like OTL Austria will demand Bavaria which they controlled most of the war. This time though, they can say they will give the Wittlesbach Naples (i.e. making them a King), which Austria figured out is too hard to defend and not worth it (at least in the Austrian Netherlands case you know it forces England to go to war for you). This would put a lot of stress on the Bourbon side as Spain would want Naples, but France is allied to the Wittlesbach. At the same time Prussia would not want Austria getting Bavaria cause it would slightly offset the loss of Silesia within the HRE. England would probably be for the swap as they most likely needed to provide naval aid to Austria to take it back during the war.