I actually found a similar harness from Umnitza and messaged them about if tapping into the foot well light will work. The reply I got back was that by using the harness will give me a error on my dash. Is there a way to get my angel eyes to light up when I unlock that won't throw any errors? 
Mercedes Benz always have had this feature and I had always found it very useful, so when I got the E53 last year,I've been trying to look for a way to have the angel eyes and license plate lights to illuminate on unlock. 
Here is the harness I found on the Umnitza website. It looks the same as the one from eas that you posted? 
http://www.umnitza.com/wiring-harnes...es-p-1230.html