Is it permissible to appoint a Muslim resident of Mecca to perform Hajj on behalf of a deceased person who was unable to perform Hajj during their lifetime, and will the deceased receive the reward for that Hajj?

The correct view is that the determining factor is the miqat (fixed point for assuming ihram) of the proxy performing the Hajj on behalf of another, not the miqat of the person for whom the Hajj is being performed. It is permissible to appoint someone from Makkah or from the lands close to the Haram to perform Hajj on behalf of your father.