I am not entirely shure I have understood Peter right. Well, here comes my reactions.
There are many ways to define groups. One of them is that everyone should do the same things; then it is a group. I do not find this definition as very interesting.
To me, one of the beauties of aikido has been that a group can consist of so many people doing things slightly differently depending on who you are. You do breakfalls if you are young and fit enough, but most people will stop taking very many breakfalls when their bodies start feeling they have had enough of this kind of traning. Young people will want to go fast. Older people might want to go slower and explore detalis. Nobody says that young people should do this and old should do that, it happens naturally and with quite a bit of individual variation. All train together, and you adapt to your partners abilities regardless of it these depend on aikido experience, age, fitness level, handicap or something else. In the beginning, you get lots of help from those you train with and they adapt to your limited capacity. In time, you will spend more time adapting to people who are less advanced. Maybe in some time more, they will have to accept that you can not take all kinds of ukemi because of how that hip operation was performed. It is OK. You switch partners regularly, so if training with the old guy was kind of slow and dull you can grab a young and athletic partner for the next technique. It all evens out in the end.
If everyone should do the same thing in the same way, then you must fit the definition of the group to be a well functioning member. Correct me if I am wrong; I believe that Shodokan aikido was formed in a university dojo setting and to me this makes perfect sense. Even though you have variation among those who come to a university dojo also, I can imagine forming such a training method as Peter describes in that environment. I can not imagine it being formed in a group with ages ranging from 14 to 58.
A group if it expects to survive must accommodate its members and make some allowance for new members - that is a given. I do believe though that individual members must strive to conform to the group not so much to become blank eyed clones but because Aikido is intrinsically a group activity. The members of the group act in concert to raise the bar for all concerned without holding individuals back.
"Conforming to the group", again, depends on how this group is defined. The more narrow definition, the smaller deviations can be tolerated.
In one of my ex-dojos, the instructors always showed techniques in two ways - with breakfall and without. It is then up to you and your partner how you train. Relative beginners and older people will generally do without break falls. Warm up is pretty simple, everyone can do it. I know of one person there who because of his interpretation of christian belief did not want to practise the sword. Although this is a dojo who does fairly much weapons training for an Aikikai dojo (som jo/bokken almost every class) this was no problem, not even for being given ranks although weapons are specified in the curriculum from 4th kyu. I do not see that this meant that the group suffered because of the individual. Occasions where the group suffer because of an individual would be when someone trains too carelessly injuring people, or just act so strangly that people feel uneasy about them, or act in a way that creates extreme rivalry and negative reactions in the group. This happens sometimes but pretty seldom.
This is another way of structuring training than the one you describe, and another way of building a group. I know of the feeling of many people doing the same thing at the same time; I have experienced it while singing in a choir, in karate and in a few other settings. This is to me not a crucial part of aikido; it has actually never been part of my aikido training. I do not see this other approach as inferior in any way. Rather, I see the benefits of more easy adaptation to age and injuries.
However, if I was put to handle a big group of newbies who do not have a clue, I would be less inclined to let them choose their own training. In most dojos though, beginners are a small flow into the main group and so they melt into the group nicely, simply adapting to how people around them do. It is a functional system.
Does these two methods of structuring training have philosophical implications, regarding personal development and such? I can not see that but then, I have never believed that aikido training implicates more self development than other activites. This is something has been debated many times. I think all things in life imply opportunity of growth. One does not need many people doing the same thing at the same time to accomplish that.
Now Peter, to what extent have I misunderstood you... :-)