why can't I change out the chainguns on the Gadus???

Yeah, it'd probably work that way.

thats a valid point, yeah.
maybe it would be designed as a cargo sub with designated layout but then retrofitted to a scout or attack sub, for example ^^

I'll try to do that eventually. Anything's possible as long as I have good ideas.
T3 Transport submarines are difficult to pull off, though, because late game barely has any outposts, so you're not getting any real value out of your cargo space.

i like your vanilla design and the creative layouts
well done again good sir.
in my next playthrough i will be using only subs from your established collection.
would you mind adding a t3 transport sub to your fleet? :) just asking.