Pretty much the same as Otto, just without his redeeming non-Catholic mother. You'd be forcing a Catholic onto the Greek throne, whether or not he would convert is debatable, and he strikes me as pretty much a dyed in the wool Habsburg arch-reactionary, so his reign might even be shorter than Othon's. Plus, there's the issue of Greece becoming a nest for vipers with all the Bonapartes, Bacchiocchi, Murats, (maybe de Beauharnais), and other, who might flock there. Although I don't see Joseph abandoning Point Breeze for a hut in Athens, ditto for Jerome cosily esconced at Trieste