I'm looking at the bigger picture - you need to look at whether those single mech lines out in the boonies have switched from standard internal structure to endo steel? If not when they are finally upgraded it would make sense to go to clan spec endo steel in the same way a lot of thrid world countries skipped over mass introduction of domestic telephones and wait straight to mobile phones. Also I'm not talking about full clan-tech mechs either - I'm talking about specific technologies that would cause other techs to be phased out. I refuse to believe that IS powers would want to have to train techs to maintain three types of internal structure rather than two once they have the capability to produce clan spec endo steel in bulk - even if they have to pay to upgrade the last couple of lines the savings both in training and logistics costs would soon cover those costs
You are right in the regard that only two types of ES are better in a logistics sense than three types of ES.
But the very great BUT is:
Only the first SL was a big fan of standardization: entire battalions / regiments composed of the same Mech / tank etc.
But now you can be lucky if you have the same mech twice in a company.
So the reality looks unfortunately different.
And to battleship technology ( I assume the wet water version was meant):
Again reality bites.
While we have examples of the old Saturn-V rocket we cannot replicate them.
Yes, we can go to Huntsville, measure them and build copies but a documentation once said that while the engines in one rocket (I believe 5 engines were in a rockets first stage) may look identical, they are not. According to this documentation each one was welded distinct from the others because of small differences in the production processes demanded that certain parts were welded (EXAMPLE!!) 5 mm more to the right so that in the end this engine would produce the same amount of thrust as the others.
And the big question:
Why hasnt it been done already?
In the Technical Readouts we find wet water ships, but they are only shortrange (AC2, LRM etc). I remember one ship on Skye. Just imagine Skye had build a battleship like the IOWA, BISMARCK, YAMATO. They could have fired from the middle of the ocean at the invading Kuritas, but they didnt do it.
The reason?
In-Game I believe that the nobles are "encouraged" by the Archon / Coordinator etc to buy good clothes, build castles but dont have a real defense force because if said noble rises up it will be very costly for the Archon etc to get control of the planet if said noble has abovementioned battleships (plural!) at his disposal. Or maybe a functional SURCOUF submarine with a big gun turret.
And if I may be so bold:
I once asked the same question where I mentioned various artillery pieces / railway guns of both World Wars and how they would translate into Battletech terms.
One answer was, that the 38cm gun of the Sturmtiger would be the equivalent of the AC-20.