From my recent use of the mod I've noticed a few things:
1) I have encountered the Kuzuryu being available for sale(mostly on the black market) more than I've encountered the Kajin, which I've only found available very rarely through production orders.
2) I've never encountered the Kurao in the wild, whether it be for sale at any kind of market, in production orders, or even a blueprint or enemy fleet
3) I've encountered the Bishamonten in some kind of shop twice, but neither time could I buy it because of my rep with the faction not being high enough, I do kinda like it being available but extremely rare in Independent military stocks.
4) Isetsu doesn't seem to like to use it's torpedoes, despite having 4 in my fleet and spending a while watching them in combat, I've only seen them use their torpedoes 3-5 times
Having seen the Isetsu's torpedoes in use though I think having variants for mounting on other ships could be fun, perhaps small and medium sizes of launcher and some small and/or medium slots on some of the smaller ships changed to universal mounts so they could use them(eg. the middle medium mounts of the Kisshoten and Gongen)