I have perhaps a better suggestion:
Once you reach faction level 500 (faction team or not), you functionally only have TWO difficulty settings, 50 vs. 500. Why not enable that third button again?
- Left button: stays at Lv.50
- Middle button: Delve record for faction team / no casualties run (whichever is lower) +10
- Right button: stays at Lv.500
Alternatively, the middle button could be a choose-your-own-level with a default value of (last successful run)+10.
Case in point: Silver Necropolis was the first Delve I cleared to Lv.500 (using a non-faction team), now I can just do the same for a pure faction team right? WRONG, I have zero ability to run the faction team at anything other than Lv.50 or 500, one of which is fairly easy while the other is probably impossible (as yet) and almost a waste of Delve tokens. And a Tuesday Faction Assault (whenever the next one is) won’t help much as I generally have to tap out after Lv.80 or so.
I am not making the same mistake with Emperinazaar faction (every 50 levels I attempt a pure faction team run to help it catch up).