You just reminded me that 90s StarCraft did have a mode where 2 players would command a single “team”. Basically a single “player” with multiple cursors. It was rad! Haven’t seen the concept duplicated.
I would focus on the economy and my brother would do the military and fight the bots.
Are you sure you aren't off by 20 years and referring to "Archon Mode" introduced to Starcraft 2 in 2015?
https://news.blizzard.com/en-us/article/19940901/teaming-up-...
AoE could do this too by both selecting the same colour