Have you seen
this collection of Sorcerer subclasses? I can't speak to whether they're balanced, but when I found it, I remember thinking "now, these feel like arcane bloodlines!"
Thinking of Sorcerers in context of
Level Up also got me thinking its reframing of race+background as Heritage/Culture/Background/Destiny. I started imagining a build-your-own-archetype for sorcerers based around a similar set of modular elements each with their own ability progressions - for example:
1. An ancestry and/or power source (dragon blood, fiend blood, angelic bloodline, ...etc)
2. A magical theme (or themes) in which they're particularly strong (maybe taking advantage of LU's broader definition of magical schools)
3. A unique casting flair or style (something affecting both casting aesthetics and effects)
4. A Limitation (must kill before each sunset, telling a lie prevents them from casting for a day, must not strike the first blow, etc - a "Wilder's block," for those familiar with the Wheel of Time)
This would really lean into the concept of a sorcerer as a rare, one-of-a-kind magical being, and really set it apart from wizards and warlocks.