the jist of it is that when you model a ship, you only do the hull model with no turrets. you would specify a location and orientation of the turret as well as the turret model name in the subsystem entry of the table. for example:
$Subsystem: someturret, 5, 1.0
$Model: someturretmodel.pof
$Position: 15,23,42
$Orientation: 10,20,0 ;euler angles in degrees, since 99.9% of modders dont understand orientation matrices, or have the patience for uvec,fvec,svec
$Default PBanks: ( "some weapon" )
$Pbank Capacity: ( 30 )
yes i know that how its parsed is completely arbitrary, how its actualy done is a whole other ballgame. nof if i were to imlement this, i wouldnt make it work only with turrets. id include other subsystems as well, such as physical subsystems, rotating parts and animated subobjects.