I remember an old Dragon article which had spell paths in it, which I assume were inspired by Rolemaster/MERP etc. I was thinking about how that would work in 5E.
So this is just random musings -- but if say "fire mage" was a sub-class for the wizard, and you get access to all fire-themed spells in the core rules (whatever class the spell was originally intended for).
Alternatively, you get access to paths as feats, and each of those feats opens up an entire spell-path to you (fire, ice, plants, whatever).
Very, very rough musings!
So this is just random musings -- but if say "fire mage" was a sub-class for the wizard, and you get access to all fire-themed spells in the core rules (whatever class the spell was originally intended for).
Alternatively, you get access to paths as feats, and each of those feats opens up an entire spell-path to you (fire, ice, plants, whatever).
Very, very rough musings!