Consciousness in the Five Aggregates is an interesting word. It is interesting because when the Buddha talks about the Five Aggregates he describes that they are processes. They are processes. One of them has to do with our body, it is our contact with the world; the other four have to do with our mind: perception, feelings, mental formations and consciousness.
The odd thing about consciousness, we could say, is that consciousness is always there with the other four; it is not really separate from the other four, even though it kind of is, as far as it goes intellectually, but on an experiential level it actually is with the other four all of the time. You won't know anything about your mental formations unless you are conscious of it. You won't know anything about your sense contact. You won't know anything about your feelings, your perception, unless you are conscious of it. So consciousness actually has to be with the other four.
Now, why the Buddha made it that way? Don't ask me, I can't answer that. And as to why some people want to put consciousness at the beginning or at the end, it makes no difference to me. The process is to understand, and if a person wants to point out how consciousness is actually there all the time, they might like to put it in the beginning to show you how important it is; somebody else might prefer to use the standard way that it is written. The standard way, I believe, is to have consciousness at the end.