There is NO successor to Civ4 BTS, the other games with the Civ name are a different more boring game. One unit per tile games are not Civ games.
Having vented, a decade ago I made a hex tile based “we-go” version of Civ (with stacks if units), got bored with the AI and never finished it. Had A* path finding, 3d terrain, economic and production models all working. Maybe in a decade I reignite the passion.