Wow, this is even more stupid than my method. And I obviously already thought of using the ledge to get there after taking a look at the editor, but the first group of ennemies alone had a dumb formation to begin with, and the second one looked flat-out impossible to get past.
And indeed, you can go through them from the edges of the screen (Which slipped my mind due to this trick being so rarely intentionally used in customs in the first place), but what a shitty triumph would be that if that really was the legit way.