A good question. The best I can do for the moment is measure what I have - the European Tesla perspective. 1 cm being 0.4 inches.
- In Europe Tesla Model S has a slight variation of the local "Type 2" AC connector in the charge port (quite similar to the common U.S. AC charger). It seems to me the overall size of the charge port opening and flap etc. are the same as in the U.S. or at least very similar. The European "Type 2" Tesla charge port diameter is around 6 cm (just the connector itself - not flap/opening is of course somewhat larger but not too much), the European "Type 2" connector being around 5.5 cm in diameter. Diameter being measured as height in this case since the Euro "Type 2" connector is not completely circular. The 0.5 cm difference in the port and cable measurements is just my inaccuracy, but to give an idea. This connector is not all that big, when build diminutively like Tesla has, although at some public chargers I've seen much more "industrial" interpretations of the same connector...
- Now, the CHAdeMO is a much bulkier story. The inside of the Tesla CHAdeMO adapter (on the CHAdeMO end) is around 7 cm in diameter and outside 9 cm in diameter, a quick measurement, the inside-outside difference isn't 2 cm but it is still substantial. CHAdeMO connectors are, on the outside, about the same size as the outside dimensions of the adapter, so even though on the inside the difference is perhaps not quite as impossible (well, it is still too big even there I think), the surrounding area of the car would have to fit a very large exterior of the connector.
So to fit a CHAdeMO directly onto a car, I think at least 10 cm diameter charge port door has to be there - and the best I think it can fit in a Model S (and I'd expect Model X looking at the mules) is that 6 cm, maybe a 6.5-7 cm if one is optimistic, and this includes the exterior diameter of the charging cable because it has to fit within the opening in the rear-light assembly.
Now, the combo connector, of course is similar to "Type 2" with simply an additional DC extension underneath, making it the size of the 5.5-6 cm diameter of the "Type 2" connector plus extra height beneath where the DC pins are. That too wouldn't fit the Tesla charge port area in my quick measurement, not even if the port was made horizontal, due to that DC protrusion.