As far as i know, no, shiny rates do not get altered based on favoritism.
At most staffers get rewarded 1 rare pokemon as compensation their work for the game. (In which case we talk about roughly half a year of active service to get the reward in the first place if staff rewards haven't changed) But the pokemon in question is made untradeable and in some cases not allowded to be used in pvp.
Free generated money is heavily frowned upon as that would skew the ingame economy.