Rather than simply slicing away the Tyrolean and Illyrian provinces, what if he completely dismembered Francis' domain and kicked the Hapsburgs off their throne?
Perhaps a Kingdom of Bohemia, Kingdom of Hungary, attaches Galicia to the Duchy of Warsaw, and creates a rump Austrian puppet state (maybe shoves it into the Confederation of the Rhine).
More important than the borders seems the question of who would rule what. After all, by 1809, he is slowly running out of brothers.
But he might be unhappy with the way Louis runs the Kdm of Holland and handles the continental system, so he might annex Holland to France one year earlier and move Louis to landlocked Bohemia(+Moravia).
If rump Austria(+Styria) remain in Hapsburg hands, their power will be broken. This assumes IMO that the marriage negotiations for the hand of Marie-Louise break down and N has no reason to protect the prestige of his imperial FIL. He might even demand the resignation of Franz I., the end of the Empire of Austria and the coronation of poor epileptic, rachitic and hydroencephalitic 16yo Ferdinand as, say, new "King of Austria". [Please don't argue that Austria alwayshasbeen an Arch Duchy. Napoleon does not care for this kind of tradition.]
This leaves the biggest area to the Kdm of Hungary, with its powerful magnates. There is no Magyar pretender in 1809, AFAIK. If the way he treated the GD of Warsaw is an suggestion, he will find a tame royal to put on the throne of Hungary, ideally one pre-ocupied with his own Kingdom (located in Germany? Bavaria, perhaps?), so while the new king supplies his name, a loyal French marshal or general will really sit in Buda and run the show.
