I must say I disagree with you. Before going to such esoteric concepts like Ki, if it exists, students have to learn pure biomechanics of the technique. It means, how to create multiple leverages on different joints, then how to control and turn the hips of attacker with these leverages, next how to unbalance him and maintain this unbalance whole way down.
Beginners have to develop a strong grip that is coming from center, not from shoulders. Such development can be done i.e. with a lot of bokken/ jo practice. Of course always there will be somebody very strong that will be able to make you work hard, but that is a point -- there is no sense to practice always with complaisant attacker.
Without such basic mechanics, where students understand very clearly each stage of technique, and can reproduce it at their will, there is no point to go further.
So yes, it is necessary to work hard with all your physical power first few years, to develop efficient techniques on resisting attacker.
Introducing Ki-like concepts only lead to distortion and watering down aikido.
Not quite true. I teach Ki principles first, along with technical. Anyway, the view of developing a 'strong' grip and relating it it bokken are interesting.
In essence the holding of the wrist is no different to the holding of a sword.
The simplicity of shihonage is that it is two sword cuts in essence also.