Has decent looks but a few things stand out to me in that trailer...
1) The use of main characters as playable characters and the laughing man logo.
A couple of the characters looked out of place in that generic armor, and Batou didn't seem to have the right body shape (he actually seemed too small I think). And the laughing man logo included worries me they're just trying to throw as much visually recognizable stuff in because it'll be the only things related to the actual series.
2) Co-op shooter game play.
I love Warframe but I've also played a couple co-op-focused shooters that absolutely blew (like GunZ 2) and if that's gonna be one, it looks like it may be boring due to small spawn waves, limited player options, and repetitive scenarios. Obviously I can't tell from the trailer, but... Let's say I'm concerned.
3) And also, I'm with the others, an FPS is a waste of the franchise. I always figured GitS was almost specifically about the other cyberpunk aspects over the violence, and removing those parts and leaving next to nothing but gunplay seems like it'd result in a shallow, mediocre and/or generic game.