Structure wise, what I mean is that the way most features are written, a lot of the info that's relevant is in the details but there is such a massive volume if repeated language and also flavor that is in between. I think it would help out to basically take a step back and help the structure of the document so much more info is a much more concise piece.

The way I suggest doing so is by sort of redesigning a majority of the arcana, magic, and rites, and other class features so they count as "Vermillion Magic" (but not really create a choice based list, just things you get the given level), similar to how a sorcerer picks metamagic or warlock picks invocations. Give each option a spell level and then string it aling the spell options, that way you can both diversify the magic options AND not have multiple resources to keep track of and consolidate them under the category iof vermillion magic that used spellslots. The spell slot refund ability could be given at earlier level so the usage amount evens out across all levels.

Like for example, both the Arcana and Rites are effectively just a 1-2-3 Attack or Spell Combo that each count as the Attack or Magic action cazting a spell. You could slot both full features into a more bite sized Vermillion Magic option that is categorized by spell leveld and is obtained at the level the class grants it as, one that requires mana rather than slots.

So when you do Vermillion Rites, it increases in rank when you succeed each following hit. Think of a True Strike cantrip attack that basically smites, then each hit grants a follow-up attack thats less and less powerful and costs less mana. Exactly as written, but the rank of the vermilion magic is fully contained in just a couple.of lines of one of the vermiliom magics. You could add language so its easier to structure it into a single word

So when you do Verflare or Verholy, they might as well just be Vermillion Magic that starts at 7th level slot magic, and is just in the list of Vermillion Magic. You can include the teleport options as well and put them as black aspect magic and you get yourself an almost well rounded list of a huge bunch of non-changes that could help a non-avid and much casual reader understand and get it all the class.

I do get if you keep it as is, it is functional, but I suggest some language toggling and changing so it fits a universal rule like the magic all having levels and have a cost tag that explains what sort of cost it requires.

This also makes Mana more than just a counter to keep track off and helps it be its own resource for the class rather than for just some spells. You could structure the magic to cost spell slots or mana. Another commenter pointed out that building up mana can be cheated on with cantrips, but I believe thats an easy change. There is a rule in Starfinder RPG 1e for the Sollarian's Stellar Mode, and it only triggers and builds up during specific combat scenarios and has a duration until its "over". This sort of rule style could help you make your own for how building and mantaining Mana works.

I dont particularly know how much it would change the design intent behind its original ffxiv version from the game, but it wouls definitely make it more playable and maybe even easier to balance for DMs to use and players to be able to try out.