If you want it to truly be like Command and Conquer:
Add more techs.
Add an Armor system.
Add directional armor to very powerful tanks(Just like what the Mammoth Tank has).
Add more units and versatility in units.
And to add on the side for people's amusement(And something very unique):
Create-a-unit. No limit to it's power just that you have to create a custom faction with it as well to use it setting your stats the way you wish for it.
Alongside that you COULD take after the game Lethal War Zone incorporating the tech upgrades where it improves statistics by 10% for health and damage... You could also add the veterancy system it has but I would prefer it to be a more HALO War's style since keeping a unit alive for an immeasurably long time and while in combat as well, would be an accomplishment in of itself(Alongside you can "Save" up to 3 veteranized units in which you can use a sort of power to call any of them in or all at once).
It would be nice... And an improvement to graphics alongside a graphics button to toggle the quality would be much appreciated since this is a very VERY old game(And as I say "Good game developers always keep going back even to their older games and improve them with what they learn")
