A check on Germany? Really? Because looking at it from an Allied perspective circa 1919, and even from my own seat, in 2008 knowing what we now know about what would happen, I would see a continuing Hapsburg dynasty in Austria or Hungary as the center of revanchist sentiment, aimed against Yugoslavia. As the Hapsburg who gets to keep Austria I would focus my attention on the Croats, who were always loyal subject in the AH Empire, and who had a vocal and militant opposition to the whole Yugoslav project. Also, with the Kaiser deposed in Germany the possibility exists that the monarchist sentiment in Germany would turn to the Austrian Hapsburg. The Hapsburg King could be embraced as a living relic of the First Reich, the Holy Roman Empire, and thus their rule over a "re-united" Germany seen as a "Restoration" of the First Reich. Plus, if the Austrian King is made the German Kaiser, he brings Austria with him, a major bonus, and actually the whole point of the "Restoration."
Really the problem with what the Allies had was that the only way to check Germany was for the Anglo-French to continue to closely monitor the Germans, or to have make an Eastern European country strong enough and with enough national interests in monitoring Germany, or to make Germany so weak that they didn't need to be monitored. They didn't do either choices 2 or 3 and failed in their duty on choice 1. They pissed Germany off, but didn't put Germany down or effectively counter Germany. Really, looking back on it, the Anglo-French would have been better off not having the Americans in the fight, because I think they would have won anyway, and when they did the peace that the French really want and the British are willing to let them impose, is so brutal that Germany won't be able to challenge France again. Wilson allowed the Germans to get off, and his insistence on "National Self-determination" created a bunch of weak little countries that were no match for Germany, and the lack of enforcement of the secret treaties created a bunch of tensions within the formerly allied camps. I mean really, what would the Americans, the French or the British have lost by letting the Italians annex the other side of the Adriatic? The answer is nothing. By not letting them annex the other side of the Adriatic they pushed a fragile democracy into the arms of the Moose.