In terms of transfer planning I think the concept is great. Signing them together is a hark back to the classic days, before international transfers were commonplace. Teams would always try to sign two players of the same nationality, language or previous team so that they would have someone to help aclimatise with in the new country. Petrov being in the same building would be a big bonus too.
You can see, for example, that Benteke and Sylla are good mates off the pitch, and Sylla has said in an interview how important N'Zogbia was for him initially settling in.