I'm intrigued by a unified subclass progression. If every class had subclass features at the same level that introduces some new ideas.
But I'll fully admit I'm not completely sold on it, if because what Subclasses are is quite different between classes. For Sorcerers, Warlocks and Clerics, subclass choice is an origin story, it's a key decision, that's why it has to be at first level. For others, it's just a specialization path. Heck my Bard PC just hit third level, and I am still weighing what subclass I should be.