To stay behind in 2024? That's the most obvious risk of timeline change. When Picard lets the escape pods go in First Contact, he tells people to find a quiet corner of the earth. I just remembered that Rios was in starfleet. But even if he weren't, does a federation citizen abide by things like altering the timeline? Or did Q basically assure off-screen that he didn't change the timeline? But if Guinan has had a photo up of him all these years, she'd know if he'd altered the timeline? No idea whether she can only sense things close to her, e.g took her a while to piece together the changes in Yesterdays' Enterprise.