Having to keep multiple pieces of armor of each element and/or switching around elements is a pain. Much better than it used to be, but still a pain.
What if armor elements were removed?
Armor mods could remain as-is. Let's say all armor starts with no element. Once a mod of an element type is inserted, the armor takes on that element type. That way armor mods won't need to be reworked (much).
This would allow the system to be flexible for builds and vault space, yet still restrictive enough to make us players have to make decisions and optimize.