I can agree Kraven would be a unique antagonist but I feel they're trying to hard to separate the new reboot from the two previous Spider-Men.
I believe that most would agree that although we do want a lot of difference in the new movie, we also want a familiar face ( or costume for that matter )
What was previously given to us with The Green Goblin was a perfect establishment of one of Spider-Man's greatest Foes.
High hopes spread when Venom was announced to appear in the 3rd installment of Spider-Man.
But as we all know, the movie didn't do so well.
So, in my opinion I believe they should reboot a more popular antagonist rather than introduce another second hand villain.