I'd allow it -- it's cool.
OTOH, be careful if he's got a weapon: you won't be allowed to use your shield against him, and if you're planning on staying in that space, you're denied your dex bonus against him. You're just begging for a crotch-shot if you stand over a guy like that.
He can definitely roll 5' away from you and stand up, provoking no AoO. You're not grappling him, after all.
Keep in mind that this is all house-rules to cover a situation not listed in the rules.
Finally, you still both threaten one another.
Daniel