When designing units, I feel the need for a Revert button, for when I want to reset my changes. As things stand, I can’t even reload the design to get the old one back.
Actually, after thinking it over some more, what I want is simply a much better unit browsing interface. What I had in mind was having the list of units on the left-hand side, with a tree structure, allowing for the easy browsing, selection, and copying of units. Something like the folder browser in Windows that would allow organization of units into chassis groups and make editing and copying units easier.