Re: Tenkan and Centrifugal Force
An example of "t"s that become "d"s would be how koto tama becomes kotodama. ("k"s become "g"s which is how the "k"imono turns into do"g"i.)
I agree that you are going to do irimi before tenkan assuming someone is attacking you. Now, whether a particular movement is called, "tenkan" or "kaiten" or even "han-tenkan" doesn't matter to me - as long as we define what we mean when we write (and it matters) then that's pretty much all you can expect.
As far as rank being meaningless in aikido - I say it is up to each teacher. And yes, some should be ashamed of themselves, but not all.
As far as there being no rank what-so-ever in a forum, like it or lump it.