Popping this idea here for reference and others' inputs. The idea belongs to Pollivar and was thought up as a means to possibly explain level restrictions in-game within lore-friendly terms while in character.
Discord log: https://pastebin.com/qRhS6CA1
The idea is thus: Level of Mindsim Integration (LMI) describes how many "levels" (the fake tally marks we all know and love) you have acquired via experience as applied within the mindsim concept. As this concept applies to all classes, it would be an elegant way of describing the niche of item level 10 not being able to be used by player level 5.
Exempli gratia: "Hey mate, can ye spare a gun? Mine broke on that ugly bugga's noggin' when I scram'd 'is brains.." "Sure. Can you handle integration level 20, though? Grabbed this off the captain." "Ahh fek.. Only got 15. Need to work on me blasted lemmi more..." ("Lemmi" being a random shorthand version of LMI I just thought of. Amusing, as you can think "lemmie use this" or "lemmie wear that". Or even think of it as a play on words for "limit".)(Edited for spelling.)