So much depends on the role he was to play, be it with Ducati or Honda (and I am not expecting him to be HRC bound) as whilst it is true that HRC have Bradl, it is also true that Bradl is not close to the times of the factory guys.
For mine, having a dedicated factory rider is a requirement (Pirro, Bradl) but if we are brutally honest, these guys are test riders because they do not have the form to be competitive MotoGP riders (in the terms of the factory guys), so in a way and not to be disrespectful they are a step below (I believe that Pirro is closer). Now this does not mean that they are not excellent at their job, they can turn lap after lap at a good pace to test the various components and what not that the factory wants.
But, they both lack that vital final step that the factory guys achieve and with the testing restrictions having a rider capable of factory guy times is beneficial in that they can test at or very close to race pace, so effectively more feedback.
problem CS has is his unique style plus availability as it is a fair question regards whether he can be used as a guide short of referencing his telemetry versus that of the test rider to see if CS' pace identified something that the test rider's pace did not. In short, he being faster found something that the slower rider could not.
For me, it has advantages but I also fully respect that the unique style makes 'trusting' him at times a challenge when the data says something else, but then, success has followed.