Is it at all possible for Tupac Amaru's rebellion to succeed, if not entirely at least in part. As far as I know, many of the indegienous people who joined Tupac Amaru's army were not completely under his control, causing them to attack both creoles as well as peninsulares, which ultimately hindered his revolutionary goals by isolating many of the mestizos and creoles.
For people who are more versed in colonial Peruvian history, is there anyone or anything that could have possibly kept the mestizos and (especially) the creoles on Tupac Amaru's side and prevent the rebellion from turning into a fullblown caste war?
Some mestizos maybe... criollos no way. The basis of their economy is exploiting those Indian rebels. To put it straight - once the independence movements hit Peru in the 1810s and 20s, most Indians did side and fight for the royalists, because the now pro-independence guys were that same criollos that had crushed them in the 1780s. And I don't think the urban mestizos of the time considered themselves to have much in common with the indians of the interior (though the few black slaves might - and TA did in fact try to gain their support in OTL).
But even if Tupac Amaru somehow
1) is able to gain real control over all the Indian factions including Tupac Katari's aymaras in what is now Bolivia, and pulls a more coherent strategy
2) he is able to perform better at the battlefield
3) and it turns out to be several strategic failures in his opponents' military strategy that are enough to overcome Tupac's limited weapon supplies
I don't see this 'new Incan empire' becoming more than a rogue state in the core of the Andes and a pain on the ass to the Spaniards for a few decades at the most. To think that all Peru can leave the Spanish empire at this point and in an indigenous dominated form is patently unrealistic.