While playing single the Great Campaign as the Reds a couple weeks ago, I had a nasty surprise.
Mannerheim had stopped my glorious and proletarian army, so I planned on repairing the dreadnough to teach them a lesson. And thus I bought replacements - something like 4 of them - for the dreadnoughs. They were pricy.
And what did my smart people do with the replacements ?
BUILD A NEW DREADNOUGH (a second element in the previously one element strong unit).
Of course, it will take one year to build it. So now my fleet is stuck during one year, and the element "not being built" is not even full strength.
As an easy solution to this problem, I believe the maximum number of elements in a major fleet unit should be one. I don't see the Reds building new warboats during the RCW - but I may be wrong on this.