Also who would be a good replacement for Pavelić as leader of the Independent State of Croatia?
A couple of possibilities:
https://en.m.wikipedia.org/wiki/Dido_Kvaternik
https://en.m.wikipedia.org/wiki/Branimir_Jelić
About the first, he and his father were pratically very influential (and is interesting he is half Jew) in the Ustashe until they have some breakdown with Pavelic albeit Wikipedia won't say how. If father and son moved to Italy TTL instead than Slovakia, Mussolini can eventually make a bet to place them instead of Pavelic.
The second, well OTL stayed in Britain, if would stay TTL as well, may be soon contacted by Italian agents to sound his options. Being a Ustashe supporter, but not tainted by the initial actions of Pavelic, can bring more sanity in the country.
And remind there is still an Italian King on the throne of Croatia... Aimone/Tomislav of Savoia-Aosta can play a role in the eventual government shift.