I'm surprised that they didn't just make this a Smallville spin-off and get Hartley back. Having said that, I can see the attraction for a totally new slate.
Wonder if this means that the Supermax GA movie is dead?
Making it a Smallville spin-off would likely carry with it a lot of weight they'd have to deal with. The first being GA's relationship with Chloe, Queen's close friendship with Clark/Superman and, of course, dealing with Superman if even only in the background.