Love the return, hate the mobile defense part.
This might be the best place to add speed up mechanics into a game mode that people dislike for its fixed time spent waiting. Don't we already have something like that in Orb Vallis? Pickups that simply speed up the process? Player power needs to be rewarded in ANY game mode with an increase of speed. Survival, Defense, Mobile Defense, Interception ... all these game modes need a way to speed up the process. Why not Excarvation? Because being able to solo defend a drill and having your team be able to split up and do several at once already speeds up the game mode. Disruption is sped up by proper communication and storing of duplicate keys, as well as sparing of elite units inbetween waves.
Just speed it up or let us speed it up and I think this will be a great return to Operation Free Forma.