I'd love to see the feature to deselect certain units and/or units of the same type from ones active selection via the UI below.
In case you did not know, this is already possible via the units themselfs:
Use <SHIFT + leftclick> to deselect a specific unit and use <SHIFT + CTRL/STRG + leftclick> to deselect all units of a kind.
Furthermore: If possible let the UI dynamicly expand or at least increas the default to a 3 by 4 grid to increase the units shown from 9 to 12.