I tried something: I've used the console command 'resetquest' and then it typed '000E38C9' (the code for the Rebuild the Blades quest) . The game didn't crashed or something like that, maybe because this is a secondary quest and doesn't affect much. Anyway, then I went to Delphine, talked to her, asked her if I can bring recruits and she told me to come with a follower. That's exactly how the quest should progress ... but when I come with a follower, I don't have the dialogue option 'I've bough someone to recruit to the Blades' or something like that :( I'm stuck here ..