Did you ever sort out the handling of the ships Xpand? I've been trying but I think some spin on collision is inevitable. Have you got a demo blend with these speed pads? They sound pretty cool!
Find attached my experimentation with force field constraints- at the minute they are exaggerated so I can see if they are working (or not!). I thought they might be useful as they can be assigned on or off (kind of like auto assist in WO HD). The only problem is the track has to be designed in a certain way to stop physics glitches but they have potential.