I was referencing some buff, orbiter strike, healing, reinforcement pods, etc being stored in "cards". The same also applies to units, since "I think" the square box will be more suitable for rts top-down game. And "maybe" the cards will allow you to show players the units' representative icon? (like you have a good frame around that unit icon? And will be able to display some info on that card like HP, Power, . . .)
And imagine if the enemy has an earthworm that eats your units from the back to cut off the supply lol. Maybe consider adding some defense towers/sentries on the path that you already occupy to slow enemy down??