Seems like a bit of a double-edged sword to me. On one hand, it becomes less likely that a single party or exploit would be able to damage the entire ecosystem

Seems like a bit of a double-edged sword to me. On one hand, it becomes less likely that a single party or exploit would be able to damage the entire ecosystem (because distinct currencies aren't likely to have exactly the same flaws). On the other hand, AFAIK, smaller networks are generally easier to attack, making it more feasible that it will happen.