One of my favorite side-step tech mods out there. To me, it inhabit the same sort of space as mods like SCAVCO or SCY.
Combining Musashi ships with Split Chamber (MHM) plus Ballistic Modernization (SCAVCO) can lead to some pretty busted combos. Heck, I put 5 Zone Scorchers (from SCY) on a Bishamonten-class and half the screen turned into flak clouds. Not too bad because that's wasting five large ballistics to pure Frag AoE damage, but still.
I do wish the Isetsu could get a tune-up, because even without adding anything to it (like no weapons, no points into cap/vent, nuthin'), it can still 'one-tap' most capitals in a single well-aimed torpedo salvo if you catch them off-guard. Rubion Torpedos are too fast to intercept, and deal a rather ludicrous of damage, on top of a ship that can not only phase but also super-phaseskip with its system in and out of any engagement. It's the Strike Ship to make every other Strike Ship jealous. 6x1500 energy damage is no joke (or 12x with EMR) If I could be so bold as to suggest something, maybe embrace the whole phase submarine aspect a bit more and make it shot single torpedo at a time? 4x single-shot tubes with long-ish reloads so you can still volley-fire for effect, but less, y'know, ridiculous? Heck, put two tubes facing back, so you can do like real WWII-era subs and shoot on retreat. Maybe steal get inspired by the Scy-Nation phase missile to cook up something that hits less like twenty tons of bricks and more like a lithe assassin?
Also, any particular reasons the Isetsu doesn't come with a Phase Field hullmod? I know it's kinda busted, like I just said, but there are plenty of mods that add phase-related hullmods whose hard requirement is Phase Field.
I also wish the Moreya didn't come with built-in Recovery Shuttles, as that gets in the way of some other hullmods from some mods (namely Martyr Pilots from FuzzyPack, which is something I run with the three Ebisu ships w/ Jizo figthers/bombers, for obvious reasons).