Viable for any difficulty setting.
I finally found a way to use storage even when playing on Master and having all mods active (such as No Kills or Knockouts, Zero Damage, No Alerts and Slowed Movement, etc).
Compared to my current 1300 points WR run you can save at least 3 minutes, if the route I used there was fully optimized. I played that level in 9 min 9 seconds then, but it can be about 45 seconds or so faster. And with this new storage route, you can complete the level in at least 5 min 20 seconds.
Go here to see the video of the full level playthrough and more detailed instructions:
This means I can now totally destroy my WR time and be perhaps even around 10 minutes faster.
(I might consider making another "tutorial run" of this route, with some things changed concerning in-game HUD stuff, such as no reticle and having the interaction prompts show. And also to show off the storage in the correct way.)