It wasn't all that hard, I literally just removed all of the offending parts, listed below.
17 striker pin for integral safety lock
27 spring for integral safety lock
39 magazine safety
65 magazine safety pivot pin
63 spring for magazine safety
And now it actually works without a magazine, though I'm not convinced that the lock for the main spring is completely disabled.
You just drift out the magazine safety pivot pin and the rest falls out.
The problem with double action seems to be either the hammer or the trigger bar.
Amusing note, I seem to have a poorly translated manual, it lists the trigger bar, part 22, as the "recoil spring bar", and the magazine safety pivot pin, part number 65, as the Axle for integral safety lock. Those silly translators.