so putting it simply as i can, in my current campaign our party has been assigned party roles that grant abilities from those roles, and mine grants my sorcerer the ability to learn all necromantic spells from all classes.

is there anyone who might know a way to make a feat that would be able to make that happen and automatically add them to his character sheet here?

Not as a feat, feats don’t have the necessary dropdowns. You can do it as part of a homebrewed copy of the subclass.

thanks for the advice!