The maximum number of subsystems (or, perhaps, the number of physical subsystems; I'm not sure) per ship is 200. There may be a limit for the number of submodels per ship as well, but it's definitely >200.
Well then I guess the maximum number of turrets is 200 minus the number of modelled subsystems.
(With up to 25 multiparts as there is a maximum of 50 rotating subobjects, if it hasn't been increased).
...could anyone confirm so that these can be put onto that wiki page?
Along with a bunch of other model related things like maximum polygons per subobject.
There are a lot of engine limitations not on that page.