Missile Specialization at T5 is kind of meh. If it unlocks a special hull mod exclusively might be more interesting.
As for 900% Militarized Subsystems, I would want a new Trader Guild's ship line for that to work.
I've been thinking about it for a couple of days and I think I have something pretty interesting and powerful to make Missile Spec worth T5. It just depends upon if I can get it to work or not. Though then I'll probably need to create some kind of special buff for its competing skill haha the cycle continues...

As far as MS, I have been tossing around the idea of letting combat freighters benefit either from the skill or from those hullmods. That alone would would give Trader Guilds, Luddic Church, Independents and Scavengers some flavor since they tend to use more combat freighters than other factions.
That being said, Trader Guilds could certainly use some unique ships and the combat freighter theme could be leveraged to a greater extent with completely new ships (which would also take advantage of that perk/those hullmods). Hmm yeah definitely something to think about more as I finish skills. That could be very flavorful and it fits perfectly with the established lore.
Very close to being done with skills now. I have to see about officer skills' elites in Leadership and Combat T5 and that's about it. Industry is done and should definitely make an Industry playthrough interesting and different from the others. Generally Industry campaign buffs revolve around loot and credits while Leadership campaign buffs revolve around defense against enemy factions and more effective combat-oriented campaign features.
Crew Training:
Space Operations:
Makeshift Equipment:
Industrial Planning:
Colony Management:
*EDIT*
Missile Specialization at T5 is kind of meh. If it unlocks a special hull mod exclusively might be more interesting.
I definitely think I have Combat T5 sorted out to be as attractive as the other skill lines now:
Missile Specialization:
Systems Expertise: (Shield Modulation is now T4 again alongside Damage Control. I think these are now good enough competitors to warrant it.)
Shield Modulation: (I'll explain why I'm showcasing this further down.)
Notice the elite versions and that they unlock hullmods. Specifically: Concentrated Shields, Safety Overrides and a new hullmod - Corrosive Warheads. Just like Localized Amplifier from Weapon Schematics Mastery, these 3 hullmods can
only be unlocked by taking the elite versions of these skills. Yup, that's right, Safety Overrides is much, much more difficult to acquire than before.
All of the the four forementioned hullmods are very powerful and drastically change what a ship loadout is capable of. It makes sense then that they should be locked behind skills rather than market RNG. It also has the benefit of helping the skill system meet one of its key goals: skills lines create unique play-throughs and create a diverse set of playstyle options. This just further solidifies that design imo.
Ok, so what does Corrosive Warheads actually do? The name does kind of give it away:
Keep in mind that the numbers are not finalized. As of this moment, the hullmod is far more beneficial when combined with smaller, more numerous missile weapons like the Swarmer, Trebuchet and Annihilator launchers. Considering that I feel like these weapons might be less used than the heavier hitting torpedoes or larger rockets like the Shockwave, I may just keep it that way.
The important thing to note is that while the particle cloud is not particularly large, it
does penetrate shields if the hit was close to armor when the shields were impacted. That alone might be worth it even for torpedo builds.
Here is a few screenshots of the hullmod's effects in action: