My suggestion is to have another fortification option, something that has the flexbility like the current "unlimited" with the strategic limitations of the current "adjacent" and "chained"
My thought is that this third option would be something along the lines of "double adjacent" or "double chained" - meaning you'd have 2 (or "triple adjacent" or "triple chained" would be 3) fortification moves.
In the current format, adjacent fortification allows ONE move to an adjacent territory, and chained allows ONE move to a chained territory... why not make it a possibility as an option to have TWO moves to adjacent territories or TWO moves to chained territories - something that is between the current one move options, and the unlimited option.