So make it a class feature. Anyone can learn Anchored Navigation, but only psions can make use of augment because their class feature allows it. Easy peasy.
It is extremely important to think about what a Psion needs to do narratively, and to ignore distractions about weird mechanics. If the Psion needs to do something that current mechanics cant do, then new mechanics will emerge ergonomically as the need arises. Dont put the cart before the horse.
Heh, forgive me for being blunt. To only allow the Psion CLASS to use SPELL augments, is a terrible idea designwise.
Either: it would require rewriting every thematically applicable spell, including duplicating clones for every new spell that is published in the future.
Or: it would mean writing a Warlock-style invocation for each and every spell ever.
Such redundancy is breath-takingly bad.
Just let spells be spells. Let spells be good at what they do well in the ways that they do it well. Spells are a separate design space.
The balance of a spell relies on how it compares to other spells in the same slot level. To entangle them too much with other complications such as class features will eventually break the game engine and destroy D&D 5e.
Spells are a design space that has survived the test of time, by 40 years of trial and error. Nothing else in D&D can handle the levels of power that spells can.
There is a need for certain new spells that need to be on the Psion spell list. But these spells will do whatever spells need to do.
Let spells be spells.