Well these are my thoughts so far. Which much of my convertion is based on the first edition of the campaign setting I am not going to dive into channeling, but keeping Defiling more or less as it is. The easy solution here was to multiply the spell level on the defiling area table by 5. Preservers spell are a class higher than the defilers, though instantaneous spells stay the same.
Mentalism goes out the window, while some lists are added to the realm of Essence or the Psionic lists. Psionics itself so far will be somewhat like it is done in SM2 (or SUC), though some old mentalism lists added to the mix (possibly even some essence spells). Other thought here would be simply going with Express#9 as with Essence and in a lesser degree Channeling. Wild talents will be roll on the table and then replace the Psionic effect with a spell (or psychic power from SM2) doing more or less the same.
I am planning to go almost full out the express #9 way, meaning all pure and hybrid using professions are put to the knife, leaving only one pure spell user for the realm of Essence (and one for Mentalism/Psionics if not using SM psionics), who then have to think up a character concept and choose spell lists based on this idea. The old profession lists could be used as concept guidelines.
The GM should first go through all the lists and decide which exist and belongs where before letting the players loose. Also some character concepts are Defiler ONLY (here I am thinking the Necromancer from Comp II) and I am still debated wheither or not Essence should have access to Elemental magic as in Dark Sun it is more or less a Cleric thing.
With channeling it is somewhat easier if you stay true to DS lore, meaning there are three types of Pure Channelers; The clerics of the elements, the templars ("cleric" of the Sorcerer-kings) and Druids. These should have a base package but still leaving a little freedom for choosing the rest of the lists. Druids could be a druid/animist mix but I havent gotten that far.
My problem with this would be the Semi spell users. So far they stay the way they are but most should probably have their realm changed. If they turn into semi psionic users then they should keep their original base lists and then choose a field or two along the lines of SUC or SM2.
All characters will have two PP ratings, one for magic (Chan/Ess) and one for Psionic powers. These will be calculated as the base PP option in Spell Law Classic, with a small change here and there.
What do you think? I have it written up as an initual draft, but havent completed it yet. But does it seem doable and managable?