Here's a type-based OM idea. Perhaps you could call it a non-type based meta.
It is:
???MONS
Name explanation: When a pokémon is typeless, it's shown as ???-type. For example, when a pure fire-type uses Burn Up, they have no types, and are considered typeless.
Premise: All pokémon have their types replaced with the ??? type. Basicaly, this means that pokemon have no resistances and no weaknesses.
(its ou based btw)
Potential metagame differences:
Pokémon with good typing like ferrothorn's will be less useful, while pokemon such as avalugg will be improved. Because of the lack of typing, pokémon only need a single coverage move. The metagame could be more defensive because every pokemon could afford to carry an extra recovery or statboosting (e.g. curse+drum+recycle+earthquake snorlax) move without the cost of coverage.
Scarf, Band, and Specs users will also see an increase in usage, because scarf-locked pokemon will be able to hit everything neutrally. Moves that do not get STAB will also see more usage due to STAB being pretty much removed.
if you can't read this randomly placed sentence, tell me.
Potential Bans:
PORYGON-Z: Porygon-Z has access to Conversion and Conversion 2, a pair of moves that are typically little more than gimmicks. However, Conversion converts the user's type to that of their first move, allowing Porygon-Z to recieve STAB (there's also Z-Conversion to make it even stronger, by boosting atk/def/spA/spD/spe by one level.) Conversion 2, on the other hand, is a defensive ability, allowing you to abuse the fact that the opponent probably has only one coverage move/ is scarflocked.
PROTEAN(especially on greninja): Protean, is well known for changing the user's type to the move they are about to use. Does your opponent have boomburst? Change to ghost. Earthquake? Change to flying, and so on. It also gives greninja access to STAB.
SHEDINJA: Wonderguard makes it practically invincible due to having no weaknesses, and it can carry a lumberry too.
QUESTIONS:
Is there any part of this that's unclear?
Are there any major flaws with this idea?
Did you even bother to read this?