Halo Wars 2 that is an RTS, but when controlling leader units like the Arbiter it'll feel like Smite with a similar camera angle. Maybe even just separate the factions and leaders into separate groups.
For example, 3v3's would be 2 players per team controlling units like they would in Halo Wars, so UNSC or Covenant or Flood or Prometheans/Forerunner, with the 3rd player controlling a single leader unit that controls like Smite. Could have a 1v1 playlist for RTS vs RTS and a separate playlist for leader vs leader. So it would look something like this:
4v4 (3v3 RTS + 1 leader unit per team)
3v3 (2v2 RTS + 1 leader unit per team)
2v2 (1v1 RTS + 1 leader unit per team)
1v1 (1v1 RTS or 1v1 leaders)
Could be interesting if this concept is evolved further. Could have AI for leader units, playlists restricting leaders so just straight up 3v3 RTS, or just about anything lol