On further thought I wasn't thinking about Ukemi (now that Atemi's out of the way). In that context, I think bag thumping may be worth looking into.
One of our typical Aikido weaknesses is that due to the cooperative nature of the venture people get sloppy in their attacks.
Different purpose now, we're setting up a situation for study.
From a strike attack to the face, a turning blend into a forearm control...
as Uke we need to attack as effectively as possible. Learning how to deliver effective solid strikes will help your fellow Aikido-mates get useful feedback on their techniques.
This is a worthwile gift I think. So punch away...