Originally posted by Jaybe
The advantage to my solution is that you can do it yourself in the editor.
Yeah, the zone of control behavior stays the same even of you make a unit with a bombard range of 2 . . . , so adding a 2 tile zone of control would mean modding the game code.
I've also noticed that once a coastal fortress is destroyed, I've never been able to build another. So, even the benefit of sacrificing a fortress to protect another improvement is a "one shot deal".
I cranked the naval bombard defense value for coastal fortress up to 24 in the editor, and then tested them vs. frigates (bombard of 3). The forts did seem to survive more attacks and did protect units and city improvements while they lasted . . . but, they still don't last very long. If the probability of the bombard "succeding" is bombard/{bombard+defense} (correct me if I'm wrong on the mechanics) or 11% in this case, then expected number of attacks needed to win is about 6. So, if the AI has a big stack of frigates (don't they always?), then the CF will not last long.
With the current defense of 8, only an average of just over 2 attacks is needed.
Even with a defense of 75, only 18 attacks are needed on average.
So, a very high bombard defense would be needed to make the CF protect against persistent attack. Eight is a joke . . .