The main rule of the TES series was "Be who you want and do what you want".
And in the series, you can always make a hybrid build, but for some reason in TESO you can only make a hybrid based on stamina and weapon damage.
But even if you decide to make a hybrid based on magic and in medium armor, through the "Pelinal's Aptitude" set, you will face such a problem that you will not have suitable potions for hybrids, because they always refer to either mana or stamina.
Suggestion: enter an ingredient that will allow you to create a potion with effects:
To do this, add an ingredient with effects
restore magicka and major brutality.
This will give the opportunity to create hybrid builds based on mana.@ZOS_GinaBruno