two different things there - the roleplay stays the same for each class, - the resonsibility grows with the power of the vessel though. the role of the character is tied to the character, not to his ship. - his responsibility to affect his surroundings and the people around him is down to hit matureness and reason.
so, - yes, a battleship captain must show more responsibility than a rhino captain, due to the fact that he affects the enviroment more easily, - but he does not need to show more or less roleplay. - a rhino captain must be as convincing in his role as a battleship captain, - but he can act a little more careless.
so, yes, a rhino captain with justice mk1 turrets can fire a broadside of his weapons for fun at someone. - the battleship captain with 16 cerberus turrets should not really do that. - however, the act of firing "for fun" is equally considered for the battleshipcaptain as it is for the rhinocaptain.
anything else would mean that we accept small ships to be ooRP, while we show less tolerance for bigger ships. what we can do is show less tolerance towards a less responsible handling of the ship. - but we should not apply a lower standard of roleplay for smaller ships.