I like it, I would keep it only to wizard spells though. (are there only sorcerer only spells or is it still wiz has every sorc spell) cut out bard, warlock for sure.
Tbh the treasure of spell books/finding teachers would determine how awesome this is... also how you plan to pump wizards (who I assume already would have had the bard/warlock spell add on).
Now will this world have artificers? FOr that matter does it have sorcerers warlocks and bards?
in my latest campaigns I am allowing 2 subclasses for your first class chosen (but not others you multi into, and for warlock you have to choose 1 of the subclasses to double so 2 patrons, or 2 pacts with same not both) I think doing that but requiring the Fighter and Rogue to HAVE to take AT/EK might work better.