Interesting notes.
I would probably do away with Sorcerers altogether in Dark Sun. The magic used in the setting is not inherent or from some bloodline. All the Sorcerer Kings are powerful defilers and psionicists who are in varying stages of turning into a dragon, not because of some inherent blood ability, but because of a 10th level spell. I'd suggest you read the official Dragon Kings original supplement to 2e.
Defiling/preserving. I am of the mind that defiling needs to be the default way of casting magic, whereas preserving is the difficult bit, requiring more skill checks or something else.
Also, remember that literacy is strictly reserved for templars or nobles in DS. No race learns automatically how to read or write their languages.