If it's anything like Trek they'd probably need massive amounts of energy to divert a FTL jump mid-flight.
Umm, no; aside from a single pretty terrible Voyager
episode (with the line "Faster than light, no left or right"), Star Trek
has never depicted it as difficult to change course during warp travel.
My impression from the Star Wars-verse (and mind you I've never given it any real thought) is that once the course is laid in that you are pretty much committed to it. Are there any examples of steering at all? Given Han's dialogue about the importance of properly plotting the course and the way hyperspace is depicted that's how I figured it worked.