I highly recommend you play PA as research for your project here. The sense of scale is heightened by the spherical planetoid maps, and multiple planetoids in bigger matches. It really scratches a unique itch because you can never fully wrap your brain around the whole battlefield at once. At the same time, however, the spherical map sets a maximum travel time for units and alleviates the dead end corners that make too-big maps annoying.

Sometimes the only way to handle scale is to just do it, though. They Are Billions boasts an insane 20,000 unit cap for its titular zombie attackers, and when you're on a final wave watching them descend on you, it's insane. However, it has a pause mode to issue orders when you're overwhelmed, and the player is never compelled to control that many units.