In halo Reach and 4 you had the option in forge to set a forge piece to spawn after a given amount of time. I think it would be very beneficial to community creations to allow forge pieces to despawn after a certain amount of time, effectively creating timed doors and stuff like that
Two Forge labels:
switch_object - object becomes a switch that players can activate
switch_delete - object is deleted upon activation of switch_object
I like this idea, it would certainly make infection games a tad more interesting. Especially if you had to survive a few doors to get to a weapon cache or something.