I don't think it's doable, although it's pretty close to it - module weapons are rendered above all of the ships if the module has a CombatEngineLayers.STATION_WEAPONS_LAYER rendering layer.
out of curiosity
in what exact scenario does this ever happen?
from my observation, module's weapons always render
below parents's weapons, however module itself can render above parent's hull
and if module has BELOW_PARENT hint, then both it and all it's weapons will render below the parent, ignoring all other conditions
in which situation could module's weapons render
above parent's weapons?
example:
parent is marked in green
module marked in blue
ring is a decorative weapon, mounted on module
tube-looking thing is a large ballistic turret
the deco mounted on module is rendering
above parent, but
below all parent's weapons
interestingly, this was not always the case, i remember struggling with this exact ship several years ago, and
then all module's weapons rendered
above all parent's weapons. which was an unwanted effect then, but i utilized it on another ship, to "fake" a module being above parent and all weapons, by simply putting a copy of it's own sprite on the module as a deco weapon. was surprised when it suddenly stopped working out of the blue.