From Patch Notes

The new item "retainer Fantasia" has been added, which allows the one-time alteration of a retainer’s appearance, gender and name.
Phials of retainer Fantasia can be obtained from the following retainer ventures:

Field Exploration XV
Highland Exploration XV
Woodland Exploration XV
Waterside Exploration XV
Quick Exploration (as a rare item)

After using a phial of retainer Fantasia, players should speak with the following retainer vocate NPCs and select "Change a retainer's appearance and nickname."

Frydwyb, Limsa Lominsa Lower Decks (X:8 Y:11)
Parnell, Old Gridania (X:14 Y:9)
Chachabi, Ul’dah – Steps of Thal (X:13 Y:9)

Phials of retainer Fantasia can be freely traded on the market and exchanged with other players.
Since Retainer Fantasia will allow retainers to change name, can we expect the same for player Fantasia in the future too?