This doesn't just punish sorcerer and isn't a "single ruleset for Sorcerer, and second ruleset for everyone else." It's "a single rule for Quicken Spell, and universal spell rules for every caster including sorcerer."
I dont see difference between those.
My Sorcerer can cast only one damaging leveled spell ... but your Cleric can easily cast two leveled heals.

And you say that is balanced?
Let me laugh even harder (
I feel like im using this meme really often lately 
)
Quicken is a much bigger problem because you can turn any spell into a bonus action. Which allows for double fireball and other powerful spell combinations without needing to spend 2 levels on Fighter (and thus be 2 levels behind on spell progression). This is especially bad in BG3 because of the lack of a long rest limit, so a sorcerer effectively has infinite sorcery points.
I have read that previously, much more than once ... and i still believe it would be unfair to limit only single mechanic and keep everything else unchanged. :-/
Normal bonus action spells are much weaker then full-action spells, so it's less of a problem to allow that for all casters.
It depends on wich level you are checking ...
Warlock that can use Hex and Scorching ray in single turn on level 3 gets 3x2d6+3x1d6 ... 54 damage ... what enemy survives this on level 3?

While he should only have 1d10+1d6 ... 16 ... still quite significant diference if you ask me. :-/
Sorcerer on the same level can with his Metamatic do 3x2d6 + 3x2d6 ... 72 damage ...
While he should only have 3x2d6 + 1d10 (presuming he will use Firebolt) ... 46 ...
And before anyone says it ... yes im aware that 72 is more than 54.

But compared to their regular (aka rule aplied) damage potential, Warlock can do more than three times as much ... while Sorcerer dont even do double.

I'm assuming that Larian also fixes the game so Haste doesn't allow the casting of an additional spell, which is unbalanced because of the exact problem above.
That is different topic in my opinion.
And I don't want to have to wade through a huge list of toggles before I start to play. I want to click on "CORE RULES" and start playing.
That is the idea im defending for last year, any time difficiulties come in some topic ...
You either pick your Difficiulty profile ... and play.
Or you then roll down to toggle options and adjust it just they way you like. :P
Just like you can do in
Pathfinder.
