I think Operation Wall Climber is the equivalent (for me) of the Gatehouse Ruins area in Elden Ring. It's an area that gave me a decent challenge at first where the terrain and layout of the ruins made finding a "route" through all of the enemies fun. There is some variety in the enemies, and then you have the knight pacing up and down and they are on a different level from the rest of the enemies. they also have a fucking spear and I love spears. I have probably cleared the ruins a couple dozen times maybe? It's always fun and I always have fun fighting the knight.

Operation Wall Climber is a pretty damn cool mission. The terrain is so cool, like there's a huge canyon that you can go down into near your starting location, so you can just pop up from below like a Gundam on a rampage and immediately destroy the turrets guarding the bridge. there's also a good mix of low buildings and taller ones, not to mention the long range defensive cannons, so you're ducking in between buildings, maybe zipping around and attacking an enemy from behind. and then there's the tetrapod which feels like the knight in Gatehouse Ruins. And then the boss is cool, a giant fucking brick with booster engines on it. And Rusty

I am so glad that you can replay the missions immediately because I've used this feature as the equivalent of "fucking off into the open world" from Elden Ring whenever I'm tired of fighting a boss.