One issue that occurs to me is the lack of atemi in grappling. I'm wondering if maybe a feint up towards the underside of the jaw or something might function similarly -- something that'll make them flinch or at least divert their attention.
Atemi might or might not make any difference. MMA events, like the UFC or Pride FC can be consulted for examples of both. Granted it's not atemi delivered by pure aikidoists, but I think the general point is accurate nevertheless.