The Mercedes engineers and ALL car manufacturers DESIGNED the oil to be changed by draining it out of the oil pan. This DESIGN was done 100 years ago. It's very simple. If you make a hole in the bottom of the pan, gravity causes the oil to come out.
The only implication of these cars being DESIGNED to draw the oil out the top is CONVENIENCE for the dealers. Until the oil draw systems were installed in the dealer service departments, most oil changes were done at the "grease pit." That was fine for PM oil changes, but what about when the oil was to be drained for a repair of some sort? Then the grease pit was not practical because the car must be moved to the tech's stall after draining in the pit. This meant a drain pan and doing something with its contents.
By putting the vacuum systems in the shops, they were not only able to efficiently remove oil for repairs, but it was as shop efficient to draw the oil from any stall where the vacuum equipment was installed as it was to do it at the pit. This meant that oil change jobs could be given to any tech, not just whoever is working the grease pit.
This whole withdrawing oil through the dipstick hole was done for dealer service department efficiency, NOT to do a better job removing the oil.
If you BELIEVE that it was done to do a better job of removing the oil, I have a bridge I would like to sell you.
For the DIY person that does not like getting underneath a car, and the dirty hands that go with it, the topsider is a great idea, but the oil needs to be changed a little more often if that is your change method. One way that you can help the topsider along, is to draw out as much as you can in the evening, then draw again the next morning to get as much of what makes its way down from the top of the engine overnight.
There is one more "downside" to the "topside," that is you tend not to make as many opportunities to inspect everything underneath. By draining the oil, you have a periodic opportunity to look around underneath for leaks, loose parts and other problems. Frequent visual inspections are as important in the maintenance of your car as changing its oil.