one of advantages of nuke submarines not mentioned here is the fact that their nukes can be launched from way closer to enemy compared to immobile nuke launcher building (that is usually in middle of your base far from the enemy) and thus arrive way faster, giving enemy little time to react in comparison, and avoid SMD cover (that often nullifies launcher nukes with their "defense shadow") by attacking from different angle, ik this doesn't matter on tiny maps that most people play on but even on 20km it seems valuable to me (yeah yeah sentons mostly)
maybe nuke submarines should instead get better at being nuke submarines rather than be completely changed into some "advanced missile ship" by giving them a more sudden and fast nuclear strike compared to nuke launchers
such as:
-their nukes traveling in a different and shorter path compared to nuke launchers, ex. directly towards target like billy does instead of going to space first like SML launched ones since they are already short range anyways to increase the speed at which they hit even more
-or even costing less to build them as they do way less damage (less than 1/3rd) compared to SML nukes in first place and having shorter range while costing the same
-or being buffed to same power as normal nukes so their cost fits instead and so they can be used vs navy as well and not just bases, one of biggest problems with nuking navy (sometimes the only way to deal with enemy navy once it gets to sufficient numbers and you can't even get in water because of it) is that it can so easily get out of the way as soon as you hear the nuke notification, which only works because of how long it takes a nuke to get to target from a launcher, meanwhile nuke submarines can hit the target a lot faster due to being able to launch it from closer, the problem is that the nuke itself is weaker while costing the same as launcher one, preventing its use against navy, the only advantage it currently has over normal nuke is the mobility of the nuke submarine and more difficulty in scouting them compared to launchers, lack of which combined with all the downsides is what makes them niche, so I suggest making them better at what they were originally for instead of redesigning them
another thing that idk if is possible, if you insist on adding this weaker and cheaper nuke to them, is the ability to build both this weaker nuke and normal nuke on nuke submarines with different build/launch buttons to allow them to be used both ways (short range billy-like and long range real nuke, with different costs)