Alt, Alt, Alt . . .

[Blackfire]

You're a maestro when it comes to dialogue so I say go with Wakka.

[Dark Link]

I guess what it comes down to is what sort of plan did you have in mind for Thief. Since he isn't really a character in the conventional sense of the term, I'm presuming you had some plan as to what his personality is like and what to add to his history.

Though he wouldn't be my choice, I do agree with the others that you would have no trouble with a character such as Wakka.

[Deadpool]

I could always choose Wakka, and then NPC Thief. Not sure I could choose Thief and NPC Wakka though.

[Ganondorf]

Choose Thief and make Money into an NPC.