>>64440614
I've been working on a design
make a ship extremely armoured and extremely fast, use her to chase down enemy ships and shrug off their missiles and so on until you're close in to obliterate everything with guns. Notably, said guns do not need to be that crazy by battleship standards, there are no battleships left to fight. (so my design is IMMUNE against her own guns; not just protected at some ranges, flat out IMMUNE.)
even though my design is approaching 400,000 t, it's a battlecruiser
or arguably a battleship. A battleship is for the line of battle, or analagously, since the line of battle doesn't exist now, it's meant to take any enemy ship in a slugging match. 
Battlecruisers though are meant to act independently and hunt down slower and weaker ships.
So, if you're the first to build one, she's a battlecruiser, and technically a battleship.
The moment the second guy builds one, yours is just a battlecruiser, because that guy probably wants a heavily gunned ship to counter yours, and he's okay sacrificing a bit of speed to do it.