This would be the first Echo zone fully created by Homecoming, so it could potentially have extra options.
If that cannot be done, a GM could be an option like in Echo DA.
The lava filled section of The Hollows is a false dichotomy. That is an underground section of the zone. Mot infested FF is an entire zone transformation, and part of a timeline.
Edit: To expand on why it could exist is the same reason as the other Echoes. True, in the mission you can clear out the enemies, yes. What you cannot do is remove the mot tentacles and bones.