Not a big thing, but it would be nice if Meta could target the Mark itself. Of course it would not change it, just increments Mark's power.
You could increment your opponent's Mark as well, but I don't see any reasoning behind it.
It would be a big buff (like, it will be an indestructible pillar in itself), but you lose 1 quanta with it (directly in unupped and indirectly in upped) and you could use up to 6.
It would help to make a trio with 2 types of pillar and Meta-ing Mark.
How about it?