Well I must say you have done your research very well and you know what you are talking about.

There is no doubt in my mind the string tension will be less than that of the classical strings if you tune down the one octave as you said. Those light guage strings will be limp as a fresh wet noodle, and you talk about easy to play, you should have very little resistance at all.

I love your idea about this. I have been toying around with some new ideas myself very similar and I already know there are some awesome tone ranges droping down in tuning. Of course this will effect the resonation of the Martin top but I think you will pick up some fantastic bass tones in that box by doing this.

As far as string tension on the neck goes, if anything you may see the neck bow backward the opposite direction beause I am sure in my mind the tension will be less and the rod will take over a little, but you can always adjust and allow for what becomes necessary.

I think it is a terrific idea and no problem on the tension. Let me know how it works out.