If they want this method to work, I'd do the following:
* Create a level 1 'alternate' feature that allows a PC to use a psicrystal rather than a spellbook and most of the wizard spellcasting section (no spellbook, no ritual magic, etc...)
* Instead, the psicrystal offers: Cantrip (as wizard), Psi - Spells known (You know 2*lvl+int spells, you can prepare from what you know, you can change a known spell when leveling or when looking at a scroll/spellbook during a LR (to the available spells only), Psicasting (ignore material, somatic and verbal components that do not have a cost for spells with a casting time of 1 action, 1 bonus action or 1 reaction).
* Add a psion college of magic and a psychic wizard subclass.
* Psion gains (Font of magic from sorcerer at 2 and everything in the psionic school from the article as well for levels 2, 6, 10 and 14.) I'm not too tied to those mechanics, so some substitution of those abilities would be good to give us more of the psion concept we know from prior editions... perhaps something similar to warlock invocations that give the wizard little psionic at-will abilities.
* Psychic wizards would be templates for Athasian sorcerer kings. They'd add the spell book on to the psicrystal at level 2, allowing the spellcaster to enjoy the best of both worlds (adding ritual magic to psicasting). At 6th they'd gain the ability to suck life force (master defiling) and store it briefly to empower spells with abilities like metamagic feats [it would be a stronger version of defiling than basic defiling if you had rules for that as well]. At 10th they'd gain a once per LR ability that has a large area of effect (a spell that fireballs a one square mile area, a spell that provides a buff like the fly spell to an entire army, a spell that teleports a structure between locations - an iconic spell spell that is very powerful in a limited way - but would exhaust the character 3 levels of exhaustion when used). At 14th they'd gain the ability to transform into an Athasian Dragon - smaller at first, but with enhanced abilities as they level until it becomes the true terror of Athas at 20th level.