I think it would be really cool to have a Secret Agent category for speed running. The main difference being that you need to complete the level with the Secret Agent rank.

Possibly, I've started routing the first level and my best time so far is around 3:40 which is about a minute longer than the usual run. I imagine the time difference gets bigger in the later levels. Saying that, I do think that having the new category will encourage more competition since normal runs have been pretty much perfected by Horned_Reaper, and I doubt they will be beaten unless you're really lucky, or some sort of new glitch/exploit is found.

I do agree with you that highest difficulty and highest rank is probably just too difficult, and getting high accuracy does depend a lot on RNG so doing Secret Agent on easy is the way to go.