Hopefully with a story revolving around war, there isn't too much for Gimple to mess up; he just needs to stick somewhat closely to the comics, and we may get the best season since number 4. My big hope is that Rick overcomes his guilt quickly, and gets on with matters, and for Daryl to use his guilt to grow as a character, he's been stuck in a boring rut since season 4.
Personally I like Negan, but I really don't find him at all scary or intimidating. He's more like a psychotic gameshow host with too much glib talk and a pearly white smile. I have read that in the comics he develops into quite a nuanced and interesting character, so hopefully they find a way to give him some depth to compensate for the lack of menace.
Regarding the Negan plot armour I think that whole RV scene was just stupid and irrelevant, basically filler because the 45 minute episode run time was just too long for what was basically just a murder scene. It was there eat time and nothing more. But I would have considered Rick a bit dumb to have tried to kill Negan at this point (which he actually did try and do) because he would have seen all his friends die.