I'm not excited to rewatch season 5 either, frankly. Apart from like 3 episodes.
I think that I'll rewatch seasons 3 and 4 first to get myself more excited.
And I definitely think that Echo will be hostile though that would truly be rich, considering what she's done to Bellamy (because of Octavia) in the past too. I hope that Clarke stands her ground though, because she should. I do think some ice between them was broken because of Clarke allowing Echo to go and save Bellamy.