The 777 is full fly by wire and it's two control columns are "interconnected", are they not?
If designers can make a complete aeroplane fly by wire through joysticks, it wouldn't be a huge effort to make the sidesticks follow each other. Where there's a will, there's a way. In Airbus' case, no will, no way.
My question was simpler - given the sidesticks are out of view of the "other" pilot, what is the problem with having a physical indication of movement being applied to the other sidestick?
In the AF447 case, the crew were apparently so confused that I doubt whether an indicator on the PFD or elsewhere of what the sidesticks were doing would have been any help. The PNF probably wouldn't have been able to register it.