Change equipment item while checked out

From [BMEC](mailto:bassmedia@yale.edu): 
> I'd like to suggest that Admins be able to change the color of the equipment while it's checked out - this way we can subvert color mixups while the item is checked out instead of having to check in the equipment, make a new reservation, and check out the equipment with the right color. We can already change the dates for equipment that's already checked out, so adding the ability to change the color of the equipment in the edit screen would be really helpful and can save lots of time (given the general loading times for the Reservations App).

This sounds, to me, like they want to be able to change which specific equipment item is attached to a reservation without having to check-in the incorrect item and creating a new reservation. This should be verified with them and we'll discuss if/how this should be done.
Does this trigger anytime @reservation already has an equipment_object set, even if the edit/update doesn't actually change it?