We're probably all familiar with the tried and true cast for each game, so maybe it would be fun to change things up a little. Suppose you could, for each Phantasy Star game, replace one person with anyone from another installment. Who would you replace, who would be the replacement, and why?
PSI - I'd replace Odin with Demi. You get similar attack abilities, as far as guns, plus some handy attack a little extra healing power.
PSII - Rudo with Rune. Kain can, for the most part, handle the gun user role. Rune's power would outstrip that of just about anyone else in the game.
PSIII - Rulakir with Zio. Zio was a much more effective villain who wouldn't have been stopped by the sealing off of the Terminus dome. He would be a more active and present threat.
I can't think of a good replacement for PSIV yet. It just has such a good cast to start with.