I think it's not a bad pairing, considering the calibre of drivers a new team is going to be able to attract.
I don't see that many young drivers that are crying out as being deserving of a race drive. Williams have signed up the best one already; most of the rest are under Red Bull's or Mercedes' wings.
At least with these two they will have a good benchmark for the car, and shouldn't lose time in testing with acclimatisation or avoidable accidents.