The problem about those side turrets here is that they are big, very visible multiparts. Which wasn't the case of the Lucy's side bombardment beams.
Not... really. The Lucifer's bombardment beams' radius is about that of a Fenris' height.
The Lucifer's bombardment beams don't actually look like beams, there's the knack. They could just as well be a completely different piece of alien technology. In addition, the addition of those didn't change that much from the original, it just added four prongs - which were also visible in all CBanims and cutscenes, and can hence be assumed to be "what

meant to do with it".
Now this Deimos has big obvious extra turrets, really shouting "I'M SUPPOSED TO BE SHOOTING STUFF BUT I DON'T LOLOLOL". They were only there to make the box art look cool, and they are not present anywhere in the actual game - look at the endgame1 cutscene, note the absence of big honkin' side turrets on the Deimos there.
Point is, I don't think you can compare these added turrets to the Lucifer's.
In the FS universe there just is no sensible reason to have fake turrets; the Shivans really are not scared away by them. In addition, imagine the load of newbies that will pop up going "why aren't those turrets firing plz help me I want them to shoot stuff".
Compare this to Fury's (nothing personal btw) main argument for having only one version: "because we can".
In short, I really think that having two separate versions is the better option. The benefits of it will greatly outweigh the extra modelling work.