PlanetsCentral

Except maybe when there is a preset rule, which we dont have.

Yup, exactly such rule we want to incorporate here. The main idea of the topic was to have such rule to avoid game lasting for years.

And the Crystal is by far not invincible. Any race can beat him with the right strategy, even the Privateer

That's not the point. The issue with your "battle it out" solution is that it benefits your race the most and can simply take too long (way too much time and effort than a regular player would like to invest in the game).