They wouldn't be 'similar,' they'd fulfill the same 'role' which is "melee ship." A boarding ship would be a fourth option (monkey wrench) outside the RPS. But, this is your show. My show is elsewhere!...   

I'm trying to see what techniques I can use to squeeze out the maximum amount of historicity and authenticity. A lot of the minor details will be wrong, but to get a broad stroke of authenticity is what I'm aiming for. Later, perhaps all of the minor details can be ironed out with subsequent iterations as the technology develops.    For instance, it would take a few more iterations to get those pleasure cruise motor boats out of the harbor and to stop all of the people on the bottom right from wearing jeans and slacks. lol Not impossible to do already currently, but I decided to move on.

With the price change, that is mostly true now. Also, they were not exactly the same to begin with anyway. But you are missing the point. What I outlined above would allow for 3 main warship types to coexist for all civs, rather than forcing the fire ship and ram ship to be so similar.

Äääähhhhhh Is that how the German wonder is supposed to look like when it's not destroyed???