Hi! I am new in this thread, sorry if I break any rule posting directly... just had this question in my head and I am sure here I can find several answers (even if especulations

) Also, sorry if I write "funny" since english is not my main language.
The background is the Christian kingdoms of current Spain ater conquering muslim territories and joining with the marriage of the Catholic kings. Them and their successors encorauged (and forced) christianisation of all their lands with the Holy Inquisition, the Contrareforma (movement lead by the church to prevent humanistic ideas such as Renaissance and Luteranism spreading in Spain), the expulsion of the Jews and also the mozarabic peoples (by their succesors), etc, etc. Basically working towards impose Catholic religion in all the territories.
Then I started wondering how things would be different if this didn't happen. I imagined a new heresy become hegemonic in a similar way as Lutheranism appeared in Germany, but as a syncretic muslim-christian religion. The, surveying a bit, I found that something similar happened:
http://digital.csic.es/handle/10261/110727. Agustín de Ribera was a mozarabic boy condemned by heresy for being a Muhammad profet during the XVI Century, but modern scholars have found that what he professed was in line with most Christians, taking elements of both religions.
Anyway, my point of differentiation starts with Agustin or a similar prophet being followed by Queen Isabel. That starts a tolerance towards mozarabics that soon takes the form of a new religion with elements of both that becomes widely accepted in Castile and Aragon.
There is where a thousand questions arise.
How would this religion be? During previous centuries Muslim countries and culture are regarded as more advanced than medieval europe, with their universities being renowned by their study of science and medicine (al-Khwarazmí in maths,
Avicenna in Medicine). This seemed to slowly change or stagnate until today (maybe I have a biased eurocentric point of view, I apollogize it that seems offensive). Europe, in its turn, was moving from obscurantism towards humanism with the renaissance and later luteran reforms which many credit the proliferation of scientifics in germanic countries. However, that didn't influence much Spain because of the mentioned Contrareforma. Would this new religion be more mystical or humanist? How would it impact philosophy and science?
How would the rest of europe and muslim countries react? Would it have any chance to thrive? We know what happened with luteran germany: a long and bloody war that however, due to political shiftings and power balances, allowed the "heretic" luterans become a established and after some time, accepted religion (or at least not prosecuted). How do you think would influence the neighboring countries and shape these two confronted worlds?
I am also curious of wether Christians and Muslims would see it as a new branch of their own religions (like suni, chii, christian or orthodox) or reject it so much and considering it a branch of the other religion.