Zioneer
Banned
I suppose the most relevant question for the Kingdom of Africa in this prospective TL is whether there is a "moderate" outcome possible in which an Almohad or other Berber rebellion happens, but doesn't result in the unification of all the Maghreb and Andalusia as in OTL; and, if so, whether that outcome can be achieved without so much disruption to events in Spain that the TL becomes more about Spain than Sicily.
Getting back to the main topic, since you seem to want a Norman-held Sardinia, have you given any thought to what that might look like? The societies are wildly different - Norman Sicily is in a sense one of the purest forms of Frankish feudalism in Europe (though less so on the island than the mainland), while Sardinia is one of the few places in the Latin world that was basically untouched by it, preserving a sort of distorted Late Roman structure for some time. Norman invasions in general seem to be adept at "wiping the slate clean" politically, but considering how difficult the Romans found it to pacify the rugged Sardinian interior I'm not sure how plausible that is for Sicily.
Well, my main purpose with Sardinia and the Kingdom of Africa (even the Baleares) is both make Sicily territorially (and resource) stronger, as well as focusing them on the West rather than the East. I don't want them to conquer the Byzantines, because then it becomes either a Byzantine or Latin Empire TL. I want the TL to focus on Sicily, it's relation to neighbors, and it's independence. I don't need the D'Hautville family to remain in power, or even the Normans to remain in power. All I want for this TL, is basically to have an independent Sicily that doesn't morph into Byzantium or whatever.
As for Sardinia itself, I was thinking that the Normans do what they did in Muslim Sicily; find an overthrown ruler (in this case, one of the jiudicates), use the pretense of restoring said ruler to slowly establish control over the island. I'm envisioning most of the traditional customs and rights kept in place, but slowly being eroded by feudalization. Basically, overthrown ruler becomes a Norman puppet, and with their help, pushes out the other Jiudicates.
It would be hard to achieve. At this point Andalusia's fate was directly tied to what happened in Maghrib and it would remain so up to the very end : a Berber power in Maghrib would at least try to swallow up the Muslim part of the peninsula, would it be only because Arabo-Andalusian elites would call them against Christians.
And giving that Maghreb at this point was "open" to any challenger...Even if Ifriqiya remains outside the general political changes as during Almoravid takeover, it would mean a stronger Ifriqiya without a real threat in West (or, inversely, in a case of a Norman deeper conquest, a good motivation for any Maghrib/Andalusian power to say hello, without that Normans being crushed as the sole conclusion, of course)
If I may disagree a bit : we're more about an "idealised" feudality, not unlike in Norman England or Yerosolemite kingdom, with a more important royal power and a more clear "feudal pyramid". You didn't have the whole lot of political/seniorial patchwork that existed in France or Burgundy at this time, with an important (numerically) nobility and vassalage, but thanks to more limited noble numbers and "rationalised" political share trough conquest (that was attempted in the Latin Empire, for exemple, but failed), and maybe as well mental changes since the Xth, didn't went the way of a feudal desintegration (as in Southern France).
A takeover of Sardinian jiudicates may be made the same way Fatimids or Italian states did in their time : making them entering the sphere of influence, with Normans eventually copy/pasting feudal and/or vassalage relationship on them (something mixed, not unlike management of Muslims entities in Latin States).
So it'd be quite difficult to keep Ifriqiya around, even if the Siculio-Normans are more successful in Africa? That any Andalusian power would pick a fight with the Normans as soon as possible, or the Maghrebi Berbers would convince them to? Hmm...
As for the feudal structure of Sicily, I was under the impression that until William II, the barons and other vassals were overly powerful, judging from the strength of the rebellions they fought. Almost every time, they managed to control the mainland and reduce the Sicilian monarch to a few outposts and Sicily. They had help from the HRE, the Byzantines, and the Pope, but the fact that they consistently managed to nearly win seems to show their strength and loose treatment.
And as for Sardinia, yeah, I think we're on the same page.
Overall though, I'm thinking of the "Norman Sicily survival" PoD to be all of the sons of Roger II to survive, so that not only are there a bunch of potential heirs (rather than relying on William I and II's ability to produce kids), but also that Sicily will have the combined experience of all of their princes (all of whom except for William were experience in governance and warfare). Perhaps quick thinking by one of them could temporarily keep the Kingdom of Africa from completely imploding, or the rebellion from being as dangerous as it was; as it was, William I could only be in one place at a time.
Hmm... perhaps the rebellion after William's coronation is butterflied away since the rebels have to deal with three very experienced sons of Roger (and most specifically Roger's original heir), rather than a neglected and passive son?