Paul, why aerobic? Three reasons, one randori and bokken/jo katas (where it really helps with maintaining a good breathing rhythm); two running away (my preferred self-defence option); three, I've got visions of living longer if I look after my heart (also see comment re potential fatman)...
Agree with you about weights/flexibility, they're not a problem as long as you train as diligently in both. However, I think you were a bit direct on Lianes comment regarding flexibility training. The more advanced moves in tai-chi and yoga (which she mentioned) do use the body as a "dead weight" on specific muscle groups for long periods at a time. For example, 5 mins in a crouch with all the weight on one leg does help strengthen the little darling, but I do agree that relying on such a regime to gain the strength in the first place is rather inefficient.