GlassJaw
Hero
If your goal is to create something that feels less like a charismatic wizard and more like soething that draws magic from the world and their heritage, I'd change the feature that makes them most like the wizard: Their spell progression table.
• No spell progression, just spell points.
• Creating a spell slot from a sorcery point requires an action.
• A spell slot that is not used in an hour is lost.
• Turn the existing spell slots into spell points at 1st level = 2, 2nd = 3, 3rd = 5, 4th = 6, 5th = 7, 6th = 9, 7th = 11, 8th = 13, 9th = 15. This is also the cost to buy spell slots.
• You can know spells of ½ your sorcerer level rounded up. Your spells known limit is per the PHB.
• Spells of 5th level or below are Lower Arcanum. Spells of 6th level and above are Higher Arcanum. You may cast 1 Higher Arcanum at level 11, 2 at 13, 3 at 15, 4 at 17, 5 at 18, 6 at 19 and 7 at 20. There is no restriction on how many Lower Arcanum you can cast other than the spell point limit.
• Each time you cast a Lower Arcanum spell, the cost to cast it increases by 1. The cost to cast a Lower Arcanum resets at a short rest.
• Each time you cast a Higher Arcanum spell, the cost to cast it increases by 3. The cost to cast Higher Arcanum resets at a Long Rest.
In general, I like this approach, although my implementation would be different.
With spell points, I would do away with sorcery points. You can spend spell points to modify spells with Metamagic. This also eliminates the need for creating spell slots (good riddance); every is from the same pool.
Without playtesting, my gut says there would need to be a way to limit the number of higher level spells cast. I like you idea of Lower and Higher tier spells. However, modifying spell costs on the fly requires too much bookkeeping.
Could simply be that a sorcerer can cast higher "tier" spells a number of times per long rest. Higher-level spells is certainly the trickiest problem to solve when converting to spell points.
But again, I wish the sorcerer had spell points instead of slots to begin with. That would have done wonders to differentiate from the wizard. I'd also like to see more thematic Origins and spell lists.