I more or less was focusing on things after the norman period, such as no Elizabeth or sophia of Hannover, and apparently more than a few matriarchal claims were pushed when needed
Your original post asks what if the Salic Law was brought over with the Norman Conquest. I was simply saying that it more or less was already. The law would have failed along with the legitimate male line in 1135.
Except William the Bastard didn't succeed peacefully and his father never married so...
William's succession was fairly uncontroversial, having the support of both the church and the French crown. The violence that engulfed the duchy was for control of the boy -- and thus control of the duchy during his minority -- not rebellion against his authority generally. William had been duke for nearly a decade before his Burgundian cousin pressed his own claim as son of a legitimately born daughter.
As others said above, it might mean that neither Matilda nor Stephen could legally claim the throne. Meaning Henry I would have to name someone else as his heir or change the law. Of course the Anarchy could still happen but Henry II (if he's born, since Matilda might stay in Germany if she isn't heiress or remarry to someone different) would have to change the law in order to succeed peacefully.
But there is no other option. The legitimate male line fails.
William the Conquerer himself may have been a bastard, but the church reforms of the late-11th century -- reforms that, ironically, William himself supported -- had redefined how society viewed bastards. So it may have been acceptable for a bastard to inherit in the days of William's youth, but it was certainly not so by the time William's son reached old age. There is no known legitimate male-line relative of the Conquerer -- not even some obscure cousin -- after the death of Henry I, and so the only option is to go through the female line. The Salic Law would be null and void. (And, again, this is even assuming anyone cared about what was "suppose" to happen.)
Henry I came under rather intense pressure to recognize William Clito as his heir upon the death of William Atheling, and he refused to do so for the simple fact that recognizing his older brother's son as heir would bring into question his own right to sit the throne -- something he was obviously desperate to avoid. He instead tried to remarry and sire another legitimate son. Recognizing Matilda as heir was the only option he had to keep his own right to the throne unchallenged.
To put it another way, there are only three possible paths for a Salic Law after the death of William Atheling:
- Henry I, for some reason, sees the law as unbreakable and recognizes William Clito as his heir. This is just extremely unlikely considering Henry I's OTL insecurities about his own claim to the throne, but let's just handwave all that way. Clito comes to Normandy or England and lives a different life in ATL, and hopefully produces a son before he dies and a whole new line of kings comes into existence.
- Henry I tries to legitimize one of his bastards -- probably his favorite, Gloucester. (I have to guess he chose not to pursue this option in OTL because of his rocky relationship with the church.)
- No one cares that it's written down anywhere. The Salic Law fails when the male line goes extinct in 1135 and is thus made irrelevant in future generations -- aka nothing really changes.