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?