Agreed, anything that looks a little odd, and there will always be some situations where they do, can usually be worked out through agreement or application of common sense in games like this.
Just cause the rules don't say you can't run over a model an infinate times doesn't mean you can.
If a driver had enough ap/movement to take a swipe at a target, turn round and come back to finish the job I don't think I would mind allowing that within the realms of common sense but yeah just allowing 1 ram attempt per target per turn seems like the easiest way of doing things.