I understand your frustration with the answers you were getting to your questions. I may have contributed to that myself on another thread when I questioned getting a black-belt in about a year. I had completely forgotten about the senshusei program in Yoshinkan aikido. I've even read the book "Angry White Pajamas", I think it was called. Though I admit I did have some questions about a participant achieving a black-belt and teaching certificate after only a year. Personally, I would not want that person as my teacher. But with that said, I think you may have already answered your own question with the research you did on the various websites you visited. They each, I believe, you said, listed the hours/days required to achieve certain rankings, including black-belt. As was mentioned by others, these hours/days are usually guidelines. With these acquired hours/days, you will usually need your sensei's consent/approval to test as well. That's the simple answer, but it does, I think answer your question as to how long it will take to get a black-belt in aikido. Your point about intensity is also well taken. The intensity of training can make a difference, but whatever system you eventually try, the minimum hours/days are usually declared for each ranking. So, if you have those hours/days and your sensei's consent, you can test (if your sensei gives consent, he/she usually has confidence that you will pass).
I think that part of the frustration you may have perceived in some of the answers you received is that, as you train, more and more, you realize that it is not always that simple. But, you gotta start somewhere.....
Man, this thread has derailed so much! And even though I felt I made such a clear point in my opening post, that this was NOT something restricted to this forum or Aikido, people seem to have taken it as such. Then this evolved into what type of training I should do before starting Aikido (where did THAT come from?), and then evolved into yet again assuming that I just want a black belt - something to this day I still don't know where people are getting from.
And yes, the book is called Angry White Pyjamas. So far I have decided not to read it, since I have lived in Tokyo before (and have become somewhat of a "foreign civil rights" activist on YouTube, in some ways). I read the book also dealt with how he viewed Japan as a newcomer, and I think that particular aspect would just end up annoying me. But I think I'll get around to it at some point.
Yes, I agree that a teaching certificate shouldn't be the same as Shodan. Certainly, being able to efficiently teach something to a student, and being able to perform it flawlessly yourself, is two different things.
One reason I have asked about how ranks transfers between dojos and organisations, is not because I'm fixated on "holding a big rank" between jumps. Rather (and I have pointed this out in the past), I want to avoid unnecessary problems in teaching for different things and grades and ranks.