is there a way to allow intelligent armors to grapple their wielder by raw?

[Urpriest]

Actually, yes, the idea that an item familiar could grapple the wielder in the case of some sort of external control sparked the question. I'll put that into the OP. (I actually forgot why I was asking, simply that I was asking.)

Ooh interesting.

There are two ways I would handle this: one if I was trying to stay entirely within the RAW, and the other if I wanted to fill in gaps with some light homebrew.

Strictly by RAW, dominance lasts until either 24 hours have passed, or a critical event occurs. Critical events are intentionally left unspecified, but the PC coming under another's control seems like it should qualify. As such, I'd have a new Ego check occur, with the results determining whether the wearer or the newly dominant item is in control. While this might seem overpowered, it's analogous to the high-ish-op tactic of letting someone else dominate you so that there's an opposed Charisma check whenever you are ordered to do something your pre-designated controller disagrees with.

The other way to think about this is to notice that there really isn't much detail in the rules about how an item that gains dominance actually asserts its will. Is it like dominate person? The description makes it sound like the item doesn't take complete control, but can do "item-ish" things to compel the person to do what it wants, like falling from their hand. In those terms, it might be plausible to homebrew mechanics for this, to fill the vacuum in the rules. An appropriate number for an armor's grapple check would probably be its caster level plus one of its mental ability scores (Charisma seems appropriate), with a size modifier according to the size of the wearer.