Well, I'm not a rocket scientist, but I did stay at a Holiday Inn Express last week ...
So here's my take on this interesting little mod.
As this car shares electronics with other Daimler vehicles, I'm fairly certain that - much like the mod I saw on (of all things) a Grand Cherokee - it's probably not that hard to do.
Note that I didn't say that it was cheap.
On the Grand Cherokee, the owner used a 2007 Mercedes E-Class start button and proximity key, which allowed him to keep the remote unlock, hatch release and remote start functions. These were all wired right in to the Chrysler electronics ... which were, of course, redone when Daimler owned significantly more of Chrysler than they do right now.
I don't know the cost of Mercedes start button, but at least there's a good starting point for this little mod.
Your pal,
Meat.