The big issue as I see it in this respect is access.
A wizard has access to 6 spells to begin with from 36 (or so) first level spells. And in the end game has access to 44 spells (or more, but DM fiat as to how, when, and what you find--after you pay to add them to your spell book) of the roughly 300 spells.
A sorcerer (now) has access to 2 spells of the 24 (or so) first level spells. But, within 2 days, they can pick ANY of them. In the end game, they have 15 spells of the 185-ish spells they can cast. At no cost, and within roughly two weeks they can replace them ALL.
Wizards are limited by what they have in their spell book at any time. And GODS forbid they lose it, it gets stolen, or destroyed! Yikes, that will cost a lot of gold to replace and now their learned spells are just the ones they have prepared--the rest are lost.
Personally, I am not opposed to the idea, except how quickly it can be done. It should be (IMO) a downtime rule, maybe a workweek to swap out a spell or something simple. shrug