Thing is, the whole setting is based around the Sorcerer Kings being defilers. There are whole works dedicated to the lore around the SK's. If you get that bit wrong, you don't really stay true to the spirit of DS. It's that one piece of lore you really need to stick to - IMO
Direct translation isn’t going to work for Darksun. We need a defiling system to be an incentive to use it. In 2e Defiling was a quick path to power. Preservers were gimped by contrast. There was sacrifice in being responsible. How do we adequately reflect this in 5e? Does DS5e need to go to spell points or use the sorcerer with the wizard spell list to represent the defiler and the regular wizard class to represent the preserver? Or is that too much? I don’t want to see defiling reduced to a +2 bonus to DC or disadvantage on a save. There is a reason the majority of Athas is a wasteland and paltry bonus does not represent it.
They didn't have contemporary sorcerers back in 2e, period. I decided to riff on the name "Sorcerer Kings" when I adapted my version of 5e Dark Sun. I realize it isn't 100% faithful to the original, but it sticks to its spirit, and it is what works for me. I used the sorcerer class as basically an arcane/psionic hybrid character class that can give a character a "slow climb" towards becoming an avangion or a new sorcerer king (if that concept interested them) *shrug*
As for defiling/preserving, I wanted defiling to be the "more powerful" option, not the "default" option. Its the "easy climb to power." By using it, you basically get free spell slots (and in some ways model having more spell slots per level as per the original rules). It, however, comes with a cost (for both flavour and balance reasons).
Good call on literacy. I should change that.
In the absence of true psionics rules, I would make the sorcerer class act as Psion (use spell points rules for it) and take away the V/S/M component aspect of spells for them.
The biggest issue would be what bloodline to use, or don't maybe... give them V/S/M free spells, maybe take some a cue from the Wizard "mentalist" class Mearls did on Happy Fun Hour.
That keeps Wizard for the "Sorcerer" Kings!