Being a GOOD UKE is extremely difficult. Counter to the thoughts of some people , a good Uke is NOT always compliant. A good Uke adjusts his behavior to assist Tori in learning. This means Uke should be better then Tori.
What type of resistance should be applied?
Take me for example, as a rather advanced student (>15 yrs), I can counter almost any attempt of a beginner to employ his techniques, I would hardly need force for that. Is this type of resistance productive? Or will it only frustrate the students to think they are learning inefficient techniques (illogical - I have learnt the same things and they would find it very difficult to avoid my or anothe Sempai employing the same technique....)
Same goes for a very week person practicing with someone who weighs twice as much, and has 30cm or more on him. (I once practiced with such a person in Randori, he kept resisting and I kept letting go for safety, at one point I did not give up, and he held his elbow for the next weeks, but at the time I had practiced 4 or 5 times as long as that guy, and it was very difficult for me).
Should the resistance be at the same speed as the rest of the practice (often slowed down for safety reasons)? or may the resisting person jump up the speed, and what would happen if Tori follows and Uke then can not keep up safely?
Resistance is not a simple thing. Which is the reason I prefer beginners not to practice it amongst themselves. It can be a good
practice when employed by a deductive advanced student to a beginner (taking consideration of the beginner limitations), or a beginner resisting with everything to an advanced student, who knows failure is an option, injury is not, provided the teacher watches such practice closely, from experience, the beginner sometimes throws himself into dangerous situations without knowing.
Your descriptions give me the feeling you were writing more about resistence, prior to suffcient pratice. This happens often when practicing with beginners: one of the common situations is them trying to "test the system" by trying to give me hardship. Those beginners often completely miss the situation for the technique, and create a state much better suited to something else. Knowing their need to feel "aikido works", I normally give them a taste of that, often selecting some more "interesting" variation
But the after this "first test", I will explain to my Uke that he has changed the situation, and that I would like to practice as sensei instructed, so would he mind to get back on course.
In some cases, too much force is such a change. For example, if one practices a technique that is only suited to
early release from side neck hold, and due to inexperience, the technique is not practiced in a dynamic situation, but rather Uke grabs and then the technique starts. If Uke were to resist with strength, the early release technique would not work, it is not suited to this situation, and a different technique would be called for.
P.S. Personally I love this testing, and definitely prefer it to those who fall to the belt (I can stand and do nothing; they fear the BB around my waist and so throw themselves at the floor anyhow, as if the belt ever did anything).
Amir