This would mostly be used in mods but what about the ability to research and implement upgrades?
For instance, researching weapon upgrades should automatically affect a weapon's stats like TU cost, Damage, etc. This could also be done for Vehicles and Facilities. This would help with adding new content into the game without littering the storage/manufacture lists too much.
Also, what about the possibility to build a new facility over an old one? Of course, the old facility wouldn't be able to work anymore but maybe repurposing an old facility instead of building one from scratch should decrease the construction time.