I was told that including atemi (strike) at the conclusion of an aikido technique was generally viewed a improper traditionally during practice. I can understand why this might be the case coming from the philosophic basis of aikido in general.
At the same time it seems like there shouldn't be some rule which generally looks unfavorably on the inclusion of some strike at the election of the tori. All the old aikijiujitsu and daito ryu finishes tended to include a closing strike. This would just seem to be a general acknowledgement of the martial aspect of the aikido practice.
The strike is to kill the uke using a knife or short sword. So it can be... Just don't do it in front of your teacher and keep it in your mind if you think it's right.