With a great interface, allowing you to easily switch from killing bugs to base management, Guardians Frontline is a great FPS/RTS hybrid with huge content potential.
Eternal Starlight is a space-themed strategy game that sees the player attempt to defend mankind's claim to Proxima, a planet representing our last hope of survival.
Skyworld: Kingdom Brawl is a real-time card fighter. It's an RTS of sorts, albeit not a traditional base-building one.