Sorry if I was a bit unclear before.
I meant to be able to change from creative mode to survival mode with /gamemode # commands. It would be in the same lobby as other people in both creative and survival mode. I think it would benefit the server by having people being able to host games that require the players to be in survival, but the host to be in creative.
Also, the spawnpoint would tie into survival. If you died while in this gamemode, you could set your spawn at a place so that when you respawn, you're automatically teleported to that spawnpoint.
I also think now that being able to enable and disable pvp would be useful. There could be a command for it, like /pvp on or off.
Catten, my post is kind of similar to that post, but not exact. There are a few differences between them