Perhaps I'm being cynical but...

Maybe its me but I had to really practice quite a bit outside of Aikido to learn to attack properly. Anyone who knows some basic striking can turn things down and do a straight punch, however learning it from the get-go in Aikido can be difficult.

Regarding attacks... Do you have a heavy bag or some pads he can actually try hitting? Is he having problem with any empty handed attack or does that include weapon work as well?

Personally I think if he and someone else were to do some very basic padwork (jab-cross-hook), then go back to doing Aikido, a straight punch to the chest would work. Or just practice doing weapons work and have him practice attacking.