It usually annoys me that TV series tend to feel the need to replace lead characters who leave, as opposed to tightening up by bringing an existing member of the cast into the spotlight. I can understand it on Stargate SG-1 because by the time it happened the four-member team was an iconic element in itself, but more often there’s already good character material waiting to be used. When the lead on Earth: Final Conflict left the show, that could have been an opportunity to unbrainwash Sandoval and make him the protagonist with a similar mission and motivation. On Stargate Universe, I’d have liked to see Greer moved up to command instead of having somebody called in from outside. Etc.