Coming up through westernized school systems and colleges, etc… we are used to courses of study being set up with prerequisites. You have to take come courses before others because without the prerequisites you cannot be expected to succeed at the more advanced material. Coming from this sort of academic environment, I think it is interesting that there are virtually no prerequisites to any aikido techniques. You can pretty much teach anything to anyone in any order. You can start in any place. You can build the system around any technique.
Nearly the only restriction on this is ukemi (falling) ability. It is reasonable to teach the non-falling stuff before the stuff that requires a backward breakfall before the stuff that requires a forward roll before the stuff that requires an airfall. But beyond the ukemi/safety consideration, each technique is a subset of aiki, an example of aiki-like motion, so anyone can improve their aiki-like motion by practicing any aiki technique.
One really cool consequence of this asynchronous syllabus is that the first-day newbie does not have to spend an inordinate amount of time banished to a corner of the mat wasting an assistant instructor's time showing them 'the basics'. Beginners can jump in wherever the class happens to be that particular day and people of all 'levels' can gain from practicing any of the techniques in the system because (here's the big secret) techniques don't matter. They are just examples of the underlying principles. Principles matter.