It's easier to change the three different cloaking devices than to introduce new ships specifically for use with cloaks. I'm not going to come in with a brand new idea and assume I'm better than Jinx and co. 'brainstorming,' because it's obviously not an easy decision to come upon. I think basing it on cargo space is inherently flawed, especially when you do introduce things like Zoner Whales and large transports that could essentially stay cloaked for a long time and act as spy ships. But a different system... well. I don't see how else it would work.