Well, we would have a good POD in 720's, when Arabo-Berbers seriously tought about evacuating Spain, but it's a bit too early.
The better way is to have the Abassids being more sucessful : In 763 they invaded the south of the peninsula and if Abd al Rahman could have been killed, total chaos follows.
Abassids in the South, Toledo in rebellion, the Asturians being hungry, the Berbers living their own life and the wali of Zaragoza as well. Once Pépin III crush the Aquitains as OTL, he would have free hands in the South, maybe making a March of Spain earlier.
The Goths of...Gothia (Septimania+Catalan Counties) would likely gain more and more autonomy, as OTL, critically with the Carolingian fighting in Italy and North.
Eventually, you could have a Gothic/Hispanic March that takes all the Ebro basin.
The Asturians would likely benefit from fight between Muslims and from the periodic pro-christian revolts to go, with a bit of luck take all the Duero basin (instead of making it a DMZ like OTL)
I recently made some map of OTL, of it can help.
EDIT : I forgot to mention the presence of a Christian principality in the south-east. Athanagild, son of Theudimer (Tudmir). Ambitious and almost independent. You could even have a junction with the Goths/Franks around Tortosa.