The only problem is of course the room in the tech tree, and the time it takes. It would represent it right to have all those in there (as it was a hectic time in Naval development) but it would really hurt the gameplay I think..
Exactly how does it "hurt gameplay"?
In the early game, almost every tech unlocks a new combat unit, yet naval combat units stay static for seemingly eons.
The way I have these units on the tech-tree you don't get a new unit everytime you advance in tech. Even if you did (and you don't), how would that "hurt gameplay"? I'm really curious to know how having these units would ruin the gameplay?
What I have setup is a NATURAL PROGRESSION of naval evolution from ironclads to battleships. Instead of jumping wildly from a combat value of 12 (Ironclads) to 30 and 40 (destroyers and battleships) respectively, you get a GRADUAL increase in firepower instead of a massive leap-frog of massive amount as the default game has.
Why is this
any differant from the gradual progression of ground units in the game? You don't have a massive leap from pikeman to tank like you do in ironclad to battleship.
You can argue it however you want, but I think you're going to have to do a lot better then blindly saying "hurt gameplay" by breaking-down the naval progression into logical and chronological progression. If anything, instead of racing down the naval chart, you can take a step, then concentrate on other matters, only needing to advance if your opponent does (or you can race down the naval path and ignore all-else).
The base techs that allow Ironclad are the same as in-the game and the same techs that get you battleship remain basically the same... the only differance now is instead of an "invisible progression" of units, you actually get to see the naval units progress as they did in history. It takes the same amount of time to get to battleships from Ironclad, but now you get the progression along the way as you did in history... if you want to make a huge ironclad or pre-dreadnought fleet, you can... or you can ignore it and try to progress to the next level... it only increases options, it doesn't ruin the game. I could say the same about just about any type of ground unit (why build a Cuirassier if you can get Cavalry if you concentrate on that path?). The choice is yours, but I call your bluff that this "hurts gameplay". That's just nuts to say that.