I'm cautiously wanting to add an addition to the idea as well for mini-quests. It could be nice to have them be deactivated with redstone (or activated.. whichever).
This could allow the use of a testfor commandblock to look for items in a players inventory and only activate the warp plate when the item is there.
I feel the original idea is very valuable but the addition of redstone interaction increases the value even more. Great idea!