Yeah a retarded Accelerator. I like him but the overall story was crap. It felt like one big long filler. Every time you think magic vs science is about to happen it never does.
While I agree that season one was far superior to season two, it still was a pretty good series and worth watching. It looks like this is something original though so who knows. Looks like it is going to at least take place after Accelerator loses his powers but don't know if it will be after season two.
I would say it is after season 2 considering that Kuroko is shown bound in a wheelchair in the trailer which can only lead me to speculate that this is true due to her getting pretty hurt in episode 7
If anything this movie just looks like original content.