If they have to replace it, then they should go back to their original idea and just add new "tours" and let people choose which one they want to go on depending which speeder they get into. I've been to both Star Tours - FL and CA - and both had a few speeders, so it wouldn't be impossible for them to run different tours on each speeder. it would also give people a reason to go on the ride more than once in the same day for some reason other than just "doing it again".