It would be able to create custom event properties from our events.
For instance we track the event property of device on all events (iphone, desktop, andriod, ipad, etc) it would be great to great a custom event property of mobile (boolean) = True (iphone, andriod), False (destop, ipad, etc.).
This would also be very helpful as we grow to understand user segments, so we can combine event properties and quickly manipulate our view of the data. We can not use cohorts for this because we want to know events that have properties associated with them not users who have these properties.