As it stand, we have plenty of Tech-Adept that would leave a secondary slot unequipped so that the primary weapon of a Construct does not get limited by it.
What this means is that ranged weapons require skill animations to work out and these animations often lock them in place (Bad for melee constructs) or prevent the usage of better primary weapons.
A secondary weapon should be something beneficial, not something you get rid of so your Construct can attack more often with its primary weapon.
To fix this, I suggest that they work like the Heavy Stubber on the Crimson Wanderer (Imperial Knight). Meaning that they have their own Cooldown etc. and can target independently and lock on enemies that are in its arc. That way Constructs would TRULY benefit from having a secondary weapon though this may be to strong on some variants and maybe become a unique Perk of the Final Tier of Constructs, the Kastelan, with its dedicated and flexible weapon arm.
That way a Melee Kastelan will fire its weapon while closing in or continue to flame stuff while he punches some dude. Or a ranged Kastelan will unleash a truly impressive firestorm, fitting for one of the most elite and advanced creations of the Legio Cybernetica.