Scissors cost more than paper and paper costs more than a rock.
I don't know about you, but I play that game with my hand, not real scissors and rocks. My hand costs the same in the form of a scissor or a rock.:)
On topic...
I also like the idea of big ships having weaker shields and more armor. It makes sense in a "realism" way as well as gameplay. The energy required to put up a spherical field the size of a BS would be ridiculously huge compared to putting one around a fighter or gunboat. There's the "real world" argument, run with it!:)
"To gain a hundred victories in a hundred battles is not the highest excellence;
to subjugate the enemy's army without doing battle is the highest of excellence."