I think that maybe we could do something like capture the flag, but go along with the Crystal defense and replace the flag with a crystal. We could make a new map that looks like crystal defense, but there would be a place at your base where you can put the opposing teams crystal down and you would have to defend it. If you fail to defend it, and the other team kills their own crystal it respawns back at their base and you have to capture it again. People who are killed would be put in some sort of prison/temporary jail that if players can reach without being killed, can release their friends by pushing a button and releasing them. This would allow them to help them capture the crystal.