Griezmann is not a top-class player or even a sure starter for us, but he has a lot of attributes that we don't have in the squad (off-the-ball movement, cheap poacher's goals, general productivity). If PSG don't get involved he can probably be had 4 cheap. Changing him for Podolski would sort our attacking midfield out for years - Griezmann, Chamberlain, Ozil, Cazorla, Wilshere, Walcott. That's the level we need to get to - depth with an excellent mix of playmaking, pace, off-the-ball movement, and goalscoring.
Not big on Balotelli either. If we lose out on Costa I don't know what Wenger is gonna do.