I'm planning to install Stilo electric power steering (yr. 2002, 127000km) to FSO 124 Pick Up. Anyone who has driven FSO knows why..
I got part from crash victim and it appears to be in excellent condition. No motor wear out or funny noises.

Before starting to hack the thing, i wondered to ask does anyone have hints about wiring? AFAIK there needs to be angle from wheels, speed, switch for city mode, or all this can be just bypassed?

Wiring diagram would be fine, I did not find it from downloads.

Has this been done before?

Hi, Welcome to the FF.

EPS wiring diagram from the Stilo eLEARN workshop manual is below. There may be some differences depending on which model and engine it's from.

You can download eLEARN from the forum downloads section here: https://www.fiatforum.com/downloads.php?do=download&downloadid=345

B1 = Engine compartment fuse box
B2 = Dashboard fuse box.
E50 = Dashboard warning light.
H35 = City button.
M1 = Body computer.
M86 = PAS ECU (attached to the PAS motor).
.

I do not think that change is possible. I think the OBD system will stop it.
It would be possible to do this with the electric assisted steering of the Opel Corsa b, from the years before 2000.
Look for the forums Opel / Vauxhall Corsa. There you may find information.