Regarding the combat level of the player could you make more mission like this by increasing the level and /or the number of bots to defeat? example x2 for MkII, x3 for Mk III ?
Mission would only be available when player has reached certain level, lesser Mk missions would also disappear from missions list when you have the required level for the next level mission.
Reward xp progression to be discussed linear less or more?

Yeah the PCC could make more missions like that, though there's a wider selection of combat XP-earning missions once you get to combat lvl 3.

Gauntlet exists because at the time it was a horrible thing to try and get to lvl 3, especially for players who had an early talent for combat as the other options at the time were dreadful to those types of players

So Gauntlet and Rogue queen were offered as a challenge/reward option

And now we also have intermediate combat so the early levels are far more enjoyable

I had considered making a higher level gauntlet but I haven't got around to it/saw a need

Remember that little 3D space shooter called descent?

You could try different difficulties especially levels called Insane, Nightmare... see the need now?