They look like fun, I would at least try them. In fact, I'd probably be very interested in a server that offered a rotation made out of this kind of mini-games.
Here's another idea: Alien Tag, where you pass it by touching another player.
Everybody spawns as the same alien class. Someone starts as it (randomly). They need to pass it away to someone else. If they can't pass it for a certain amount of time they are eliminated and moved to spectators. Last player wins.
Works the other way too: gotta keep it from being taken from you. If you manage to keep it for a certain [consecutive?] amount of time you win.
Obviously, needs maps that aren't too big and have no strange quirks. I feel it would be a lot of fun with maras and goons, hilarious with grangers and could even work with rants. I'm not sure about dretch since it's too small and agile, and I'm kinda torn about basi.
In case it needs saying: no building, no structures, only indestructible eggs scattered around the map. But you could add an RC/repeaters and a few (indestructible) turrets spread around the place, just to make things more interesting.
Not sure if it's possible to have a game without any humans/nodes in it though. I suppose you could hide a node somewhere and lock the human team, while allowing the alien team to get any number of players.
There the question of whether to reset the "it" counter for a player every time he loses it, or cumulate the times. Cumulative times are easier to achieve. Depends on how long you make the time. I believe Carmageddon used 2 minutes and cumulative times.
Obviously, you'd need some way of displaying the running time on the player's HUD.
