A HUngary gaining its independence in 1848 would be very different than you imagine. Firsrt and foremost Croatia wouldnt be a part of it. In 27. august 1848 the hungarian parlaiment voted for the complete independence of Croatia from Hungary. This wasnt enough as a habsburg-croatian army crossed the border on the 11th of September attacking Hungary. There was never a question during the revolution of Croatia becoming part of Hungary.
Second the leader of this Hungary would be Kossuth. Thats a huge change. He was the only important hungarian politican who wanted peace with the national minorities - the Danubian Confederation was his idea. But that was after his tour in the USA and heavily influenced by what he saw there.This wont happen if the revolution succeeds as he wont go to America.
The problem is that he was pretty alone in this regard. So i have no idea what would be the policy of Hungary toward the national minorities after a successful revolution. I know what Kossuth wanted but every other leader was against him. However his influevce was huge....
However i dont see in any case them being unfriendly towards the ottomans. Hungary would be a supporter of the Status Quo in the region and view Russia as his main enemy. In this Kossuth and the rest of the elit was united.
I am not sure if he wanted peace with the minorities per sé, but he wanted the Danubian Federation of Hungarians, Romanians and South Slavs to inherit the regional dominant role of the Habsburg Empire. (BTW, as federal parliamentary language he envisioned either French or German).
It is very obvious that this would completely thwart all Russian ambitions on the Balkans and towards the straits. Fur Russia it would be a casus belli, and to pursue the creation of such a federation would mean robbing the Ottomans and provoking the Russians. Hungary would be in a position similar to A-H in OTL, only weaker.
In the case of Hungarian independence in 1848, what would stop Russia from trying to vassalize the Danube Principalities and declare itself the champion or Romanian, Orthodox rights in Transsylvania?
There might be a Romania-centered parallel to the Crimean War in this TL.