I propose a mechanic that would finally allow the player to swap the position of units directly without having to move one unit into an empty space first.
Zone of control rules would still apply so you can’t shift units along the line too easily. However, where zone of control permits it, units should absolutely have the ability to swap positions.
I imagine it to be similar to how this was handled in Civ 5, where you order unit A to move into the space occupied by unit B, then click unit B and order it to move into the space currently occupied by unit A.

Btw, I think you guys are awesome for giving the community a chance to give some input early on