I had a similar idea for a wholesome Celestial Warlock recently. Remembering a bit form some stand-up comedian in the 90s; with schizophrenics, why do the voices always tell them to do bad things?
Character is an low-key Aasimar, but tries to hid it by being all goth. They were mostly ignored by their family, like 90a latch-key kid.
They try to act all dark and edgy, but they constantly have their bright and chipper Celestial patron whispering in their ear to do positive things. Played like the Bowler and her dad in Mystery Men.
“You should really help that orphan find their real parents.” “You HAVE to rescue the princess!” “Hey, help that old lady across the street.” “You don’t need all their gold as a reward, you should leave them at least half.” “Hey. Hey! Tell [party’s druid] that she really looks cute in that outfit.”
Could also work with Divine Soul Sorcerer, with their angelic ancestor whispering in their ear.