Working with weapons really opens up your mind. For an art like Aikido, reliance on empty hand techniques for practice but raving on and on about how we derive our art from the sword and spear is ludicrous.
Adding weapons Enlarges the scope of your training. It creates a tangible element to increase your awareness of intangible concepts like maai and chushin among others.
By using a weapon for both uke and nage, they create another layer. Whereas with the empty hands they only have their hands and body to worry about. Thus with the hands so closely attached to the body, most nage don't realise that they are too close or too far from nage. With a weapon, immediately the tool shows them of the effectiveness of their distance and positioning. It's like an Aikido ruler and leveler all in one.
There's also a paradox. With weapons uke tends to engage nage better. It's as if they are empowered and override their fear to engage nage properly with an attack. Perhaps the length of the weapon encourages them to attack properly because they feel less threatened. Shorter hands means hat nage accesses their body too easily. With weapons, there is now this tangible extra distance that they get. Interesting, convincing, but in reality there's no difference.
Training with weapons also teach both nage and uke superior positioning and when the end game has arrived. At which point where recovery is none existent. And before that point arrives, what can be done. As you do better, that point gets lessen to the point where it's none existent at the point of attack. But the discovery to that alone helps speed the process of learning.
Obviously the weapons you use will to a certain extent dictate what training you can do. Equating a Jo to a sword to a knife is like saying a skateboard, a surfboard and a snowboard are one of the same.
No one expects the training to be an Indepth mastery of the weapon though. Learning with weapons is meant to enhance the Aikido training, not teach you mastery of the weapon or over the weapon. In some respect realists will question the validity of that training if it doesn't accomplish either. Might it be that the training is then just self gratification? A delusion cooked up by men wearing skirts to validate their martial efficacy?
To a certain extent, anything going on the modern dojo would probably be closer to delusion than the reality. The fact is, most of us have no combat experience and are unlikely to get one anytime soon. Nor are we teaching special ops on the use of knives and swords on the off chance they meet a group of super ninja villains that dodges assault weapon fire with ease but die comparatively easily against some fancy kicks and knife throwing skill.
It is enough that the weapon creates focus ap for the training that we do. If we understand that aikido principles are applied regardless, we stand the chance to use those principles when there's a need for it. Since we are followers of a Way, it suits us to train this way.