First millennial Catholics would have been taken aback by the papal appointment of bishops, but they would have been utterly shocked to learn that someone who was already the bishop of one diocese would accept election to another.
Such a practice would have been recognized as in direct violation of the teaching of the First Council of Nicaea in 325 (a council that defined the divinity of Jesus Christ and gave us the Nicene Creed). Nicaea's teaching was reaffirmed by the Council of Chalcedon in 451 (a council that defined the relationship between the divinity and humanity of Christ).
Canon 15 of Nicaea read as follows: "On account of the great disturbance and the factions which are caused, it is decreed that the custom, if it is found to exist in some parts contrary to the canon, shall be totally suppressed, so that neither bishops nor presbyters
nor deacons shall transfer from city to city.
"If after this decision of this holy and great synod anyone shall attempt such a thing, or shall lend himself to such a proceeding, the arrangement shall be totally annulled, and he shall be restored to the church of which he was ordained bishop or presbyter or deacon."
http://ncronline.org/blogs/essays-theology/transfer-bishops
Unless a diocese is in absolute need of reform, why not appoint a local priest as bishop. I'm rather uncomfortable with a corporate model of Church that moves bishops from small dioceses up to the big leagues or that uses small dioceses as rewards for the Cardinal's staff. For example, I think the time Syracuse had a local man as bishop was 1987.