If you want to control units, the engine offers a first person mode. So you can squad up with your friends (share units) by using the "Invite to squad" button in the Tab playerlist. Then they select their unit and enter /ControlUnit into chat. This should put them into first-person unit control mode.
A warning before you try it though. It's an old feature that has never been really well tested or used. When it works it's still very clunky and not really enjoyable to play IMO, but I just wanted to let you know it exists.
So honestly, you might be better off looking for a game that focuses on FPS/RTS interaction. For example
Eximius is a game focusing on exactly that.