The film actually looks like it's exploring an alternate timeline / prequil period. If you've seen the recent OVAs (GitS Arise) this could be an alternate view

The film actually looks like it's exploring an alternate timeline / prequil period. If you've seen the recent OVAs (GitS Arise) this could be an alternate view of what 'the major' looked like before she became the team lead we're more familiar with in other movies and series from this fictional universe. In a time when she is still a slave of 'the system' (I mean that more in the military/industrial/political greed context). Having made that speculation, I'm not sure that's where this movie actually is. I hope the trailer is simply trying to convey the genera, art-styles, and beginning of the plot (without too many spoilers); but I'm used to trailers that pretty much spoil everything except the culmination of the film.