I think it goes against the spirit and tradition a bit. If you are good enough to challenge for the top 10 GC places then surely you shouldn’t be riding for someone else.
While a big paycheck may encourage potential GC contenders to subjugate their goals for another one, their own ambition and desire for a clear place in the history books should work against that. We've already seen Simon Gerrans leave Sky to GreenEdge, Rigoberto Uran to Mega Farmers and Richie Porte go to BMC in search of leadership for GC assaults, as well as Cav switch to the Mega Farmers in the hope of more sprint support.
Or at least there shouldn’t be more than one “superdomestique” in each team. One as a wingman, sure, but surrounding the leader with riders who should be leaders of teams themselves, and not really going for any other stage wins or anything? I just think that’s against the spirit of the competition.
GC riders pretending to be superdomestiques don't usually seem that helpful: Valverde "for" Quintana, Nibali for Aru (that one seems genuine even if it's not been so effective - I assume Nibali is secure about his plans for next year), Teejay with Porte, Hinault "for" LeMond
Sky seem better at convincing them (maybe it's "do this for the team now and you will be our protected rider at a later grand tour"?) but even Froome supporting Wiggins wasn't exactly harmonious. Thomas for Froome is about the best it's been, isn't it?