Conradin was widely popular in Rome, not the pope, but by the masses.
I think after the victory he would need to :
1 consolidate his Sicily and Italian holdings, this was the wealth of his territory
2. Become emperor of of the Romans. Get a new supportive pope, and giving the pope control of german bishops , thereby gaining the popes support, and keeping the hre in some chaos. Also pull support from Latin remnants in Greece, allowing the ere to gain srenght
3 from here he would need to use this wealth to keep and expand his german holdings, delay the election of the hre.
4 use his army to crusade in Tunisia and Algeria, wealthy provinces.
5 as a successful crusader he would be in good stand to become the hre
6 if not the hre he could then look at campaigns in Egypt with a trade for someone else to be hre for massive military support