I saw a few misconception about the Revolution in Austria (and especially Hungary).
Austria would've been victorious even without Russian help thanks to Radetzky defeating the Italians. In hindsight, begging asking the Russians for help was one of the worst decisions of the time. It did, however, shorten the war by a few months and allowed the Austrians to keep troops in Italy and maintain their influence there. Which, again, isn't much in hindsight...
I also don't see how the Hungarian Diet could've recalled the Hungarian regiments from Italy. Not in time, at least. First, they were loyal to Radetzky and the very small number of defections (including Italian troops in the Imperial army) shows that. Second, remember that hostilities only started between Austria and Hungary in the winter of 48-49. Before that, the fights were between the Hungarian Diet's forces and Ban Jelačić's forces, neither under Vienna's orders. In fact, Vienna repeatedly tried to settle the conflict, but Jelačić got cocky after his initial victories and the Hungarians were becoming more radical as Minister-President Batthyány became weaker. It also didn't help that Austrian officers fought on both sides, often received confusing orders, and all believed to be loyal to the Emperor/King.
In my opinion, the only way to make 1848 succeed in Austria is to keep it peaceful. This can be succeeded by Count von Lamberg not getting murdered in Pest. Or, better yet, him not getting unconstitutionally appointed in the first place. His murder was arguably what led to Vienna fully turning on the Hungarians. I believe that if Vienna doesn't intervene, the Hungarians eventually defeat Jelačić and push him back to Croatia, but are unable to retake it. So, Vienna then brokers a peace between Pest-Buda and Zagreb. The results depend on when Vienna can convince Jelačić to stop messing around. If he realises early that he can't take Pest, then Croatian autonomy should be acceptable to the Diet. If not, well, it'll be complicated. Likely an 1869 Croat-Hungarian settlement-like deal.
Or, the Liberals in Vienna are more succesful and keep the Kamarilla from retaking power. This will likely lead to some awkward legal issues with a constitution for Hungary and another for the rest of the Empire, but that's almost the 1867 agreement anyways. I assume some kind of agreement over foreign and military affairs would be acceptable for the Hungarians since the April Laws are really short-sighted over them. As long as the April Laws are maintained (and this is seriously important!), there should be peace between Vienna and Budapest.
Anyways, the consequences of a succesful 1848 in Hungary are pretty significant, especially if things don't devolve into the confusing mess of 1849. Basically, the boom Hungary went through after 1867 begins in 1848 instead. As was thoroughly debated between '41 and '48, the customs barrier between Austria and Hungary is abolished, increasing trade significantly. The Hungarian politicians are also more reform-minded than in '67, so the Laws on Minorities could still be passed by the Diet, making Hungary potentially far more progressive than OTL post-1867.