Sorry for bothering you.
I think it was done to reflect 'historical accuracy' more, i.e. nations who had no access to the sea don't have ships. I like imperia, but this is one of the weak points because it creates 'unfair' situations to play vs nations who do have these ships. Then again, imperia was build for single play and never intented for online play.
On a side note, the [1CB] clan is making an update for Imperia, perhaps they will reinstate this. There should be a beta version out any day, and a full release this summer, so stay tuned.
Alternatively, you can add the ships back in to the nations yourself, it's not that difficult, and since its a single play mod, there isnt much that can go wrong.