Control is itself an objective number without assumptions beyond a shareholder-list / Cap-table. Control is literally the percent of all possible outcomes in which the result of the vote/election is decided by the shareholder's vote.
In the link you will find a second graph, in which I give the chances of winning a shareholder vote. Here there is an assumption that each shareholder is as likely to vote one way as another. There is no doubt it is a softer number, but I report it because people can understand what it means much faster than control.
Now these issues of psychology and feelings about particular issues can be accounted for, as you can imagine its necessary when working on the activist situations we cut our teeth on, but there we generally have public statements about which way particular shareholders plan to vote, or how they feel. When looking at a founders long term control, its best to leave out these issue. Less good information is better than more so-so information.
If you want to know a about founders ability to do something specific that would polarize shareholders around common interests, such as sell the company at a price that is personally rewarding, but not great for the investors, that calculation can be done. I just think it should be thought of separately from a founders general control.
Sorry for the length and hope this helps!