While I see your point, especially for top guilds.
And something has to be done to Surge, so that everyone feels useful, and get s a chance of earning gold.
My guild has a rather wide range of member power levels probably ranging from 200K to 600K atm.
So while we don’t clear Surge daily, we do have real problems with lower power members having a hard time.
Mostly because some are not able to clear anything but the easiest regions.
The reason is the way Surge difficulty scales to Guild Total power, or what ever the metric is, and that not all players are equally active.
Those that are a little less active or spend a little less money will slowly get behind on their ability to earn Surge gold under current Game Mode mechanics.
While we have had success in the past with trying to teach members to be considerate when choosing both target Districts and which Mercs they hire.
This is becoming increasingly difficult both as the power gab between top and bottom members increase. But also as we are getting more new recruits at a faster pace, so we can’t keep up with teaching them Surge Team Play.
TL:DR
All of this is to say, that adding another difficulty, ant least with the current reward scheme for gold, would be great for top players and guilds.
But it would just make the real problem of this game mode’s rewards being lopsided, even worse.
As I don’t have any real suggestions for improvement, I guess I’ve just wasted everyone time.
Maybe adding the extra difficulty like OP suggests, but cap the real rewards where they are atm, including not adding more gold rewards. And instead give some kind of guild Bling rewards for clearing this extra difficulty.
i.e. a watermark “‘Star’ 5” to the guild Profile image (5 being the number of times that difficulty has been cleared). Or some other visual, but otherwise useless goodies.