I don't think this would help much.
As I mentioned before, my main problem with Mobula is its lack of maintaining both repairs and firepower together at the acceptable level, especially considering that both its hull and balloon can be easily damaged simultaneously with the Hades, which is good against one and decent against the other, to make matters worse. Apart from Hades being popular, dealing damage to both main components on the mobula actually goes for every gun in the game other than Merc.
If you want to have good firepower, you have to let the balloon and hull go (and we all know that never ends well for a ship).
If you go for repairs, you end up losing one gun per damaged component, leaving you with either 2 guns shooting (if pilot is the one to mount the top gun) or 1 gun and ship's maneuverability.
If we go for giving up the top gun, you already cripple mobula maximum damage potential of 4 guns shooting at once, it does get a little bit more survivability with pilot being able to hit it with a wrench/mallet once in a while (where he gives up maneuverability for a second), but one tool is not enough to keep it maintained. That means one guy from the side guns needs to go and keep it maintained properly, which cripples the maximum damage potential again, but I would even say for longer time than it is the case now. And god help you if balloon needs repairs too, you end up with only one gun shooting, back to square one basically.
In case of most of the ships, you have either one engineer highly devoted to keep the repairs going for the ship(Galleon's Main Engineer), or you have an engineer that has a way to keep the main component healthy fast enough after shooting a gun(Junker's Front Engineer, Goldfish's Starboard Engineer). In some cases you have both on one ship (Pyramidion's Main Engineer and Balloon Engineer), in others a pilot has ways to help with the repairs of the component in a critical situation (Galleon, Junker, Spire), but the problem is, you have none of it on the Mobula. Mobula can be damaged too easily to stay on guns and not worry about the components, but components are too far compared to what you have on the other ships, and they can't be maintained as well. They are too far from eachother to have one engineer fully devoted to the repairs, and pilot cannot help with the repairs either.
Funny thing is, I don't exactly feel that it's as bad of a case for the Spire (TFW you call Spire more tanky than Mobula). Spire's guns are much easier to maintain in arc (for it doesn't turn as much as Mob), giving the pilot more freedom to either mount the light gun next to him, or to help with hull repairs. Maximum hull armor is lower on Spire, but as in the Squid's case, it rebuilds so quickly that you can actually stay alive for quite some time, whereas Mob engie has to spend quite some time to rebuild the hull armor. The most important thing though is the fact that the Spire has a heavy weapon. Mob's guns can be easily ignored, for two light guns (or one, depending on how you play mob) can't cause a damage as devastating as merc/hades and h.flak/LJ, and there's no problem ignoring mobula's fire if you harass it hard enough to give the engineers some work. Spire, on the other hand, can give you a hard time even with only two people mounting the guns. Not to mention that, from my experience, enemy's shots don't go for the balloon as often as they do for the hull, already giving the Spire an advantage over Mob, where you always deal damage to both main components.