Lol, it's not that he wants a Psychic TrickScarf lead. It's more like, most of the pokemon that learn trick are psychic. Psychic isn't that amazing because of the higher possibility of U-Turn ruining Trick and Tinted Lens BugBuzzes.
Latias just has good resistances (I tend to think ... mainly that electric one is what separates it from others). Starmie isn't used nearly as much, but it does have a good ice resist for your dragon to have an easier time setting up. Trick leads are (generally) more about having the right resistances and weaknesses combo with the set up pokemon in the rest of your team.