I did measurements on ignition switch wiring
Wire colors - pin number in socket - function
2 wires in Red - pin 30 - 12v constant power
Pink/green - pin 15X - Ignition #2
Pink/red - pin 15 - Ignition#1 (On 1)
Green/white - pin P30 - There is 12V in this wire until you turn key into Ignition 1 position after that there is 0V
Pink/yellow - pin 15R - ACC
Violet - pin 50 - Start engine
I have bought "Car Engine Lock Ignition Starter/Keyless Engine Push Start Button/RFID System" form Ebay. This device has 6 wires to connect to 12V, GND, On 2, ACC, Start and On 1. So now you know how to connect this think.
Another issue with this push to start is steering wheel locking. The key blade should be left in ignition switch and turned to ACC. Therefore there is constant power drain from battery. The best solution is cutting ACC wire and installation of simple rocker switch in case one would like to operate ignition switch as usually.
The last issue is transponder. I disconnected transponder coil from Siemens module located behind cluster panel, then I extended it's wire reconnected it and put this coil in box close to cigarette lighter. When you put key fob in it, it works as before.
I update post with some pictures as soon as I make them.
To be honest I have to say that I used some instructions from "Remote Start, Push Start and Keyless Entry Install Write Up / DIY" on Benzworld site in section of W163 M-Class