Shed-on-a-Pole
I haven't checked the THY timetable for specifics but would not expect a problem with this. Transatlantic flights departing from IST are highly unlikely to clash with MAN's overnight and early-morning stand congestion. Late morning and early afternoon timings should represent no problem at all for stands.
Are they likely to depart earlier due to the extra couple/few hours they will be on the ground en-route for security checks?
Two or three hours earlier into Man could cause some problems with free stands.
If they arrive a few hours late ALL connections will be missed. I have no idea how many PAX this would involve but it could create some big problems on the U.S side.