I haven't read this entire thread, nor do I have a full understanding of the TOI philosophy, but based on what I have seen and heard, and since I was asked to provide input, I think the following thought experiment (or actual experiment if you have access to a table and have some patience) can be helpful:
With a center-ball aim,
1.) slight error to the inside results in a TOI (touch of inside).
2.) no error results in a pure center-ball hit.
3.) slight error to the outside results in a TOO (touch of outside).
With a TOI aim,
4.) slight error to the inside results in more than a TOI.
5.) no error results in a TOI.
6.) slight error to the outside results in either a pure center-ball hit or a slight TOO.
The real question is: Are 4, 5 and 6 better outcomes than 1, 2 and 3, in general. I personally don't think so, and there are clear and solid arguments that back up this viewpoint.
For straight shots, especially long shots with tight pockets, an attempted center-ball hit will obviously result in the most accuracy and consistency (unless there are
problems with visual alignment).
For cut shots, the choice of inside vs. outside will often depend on CB position control requirements, so we don't always have a choice. If there are no english requirements on a cut shot, an argument can easily be made for either a touch (or more) of either inside or outside english. I think for most people (especially those who don't have a solid understanding and/or intuition of all important
effects involved with aiming with english), no english at all will be the most effective choice, assuming the person isn't relying on english to help correct faulty aim or visual alignment. And for some people (especially under
clingy conditions), outside english will be the best choice (especially if one knows how to judge the
gearing amount of outside english appropriate for each cut angle).
For those interested, arguments supporting the use of inside english can be found on the
inside english resource page, and arguments supporting the use of outside english can be found on the
outside english resource page.