Sorry if I mislead anyone. When I say reschedule I mean the airline who does the rescheduling. When I need to change my flight, I would call that "rebooking" (that's what I saw on SQ and CX website with that rebooking fee).
It is very simply, I book Cathay Pacific to Taipei, need to transit at HK. The CX to HK plane got delayed, they sent me to an SQ plane. Even if they do not send me to an SQ plane, they would reschedule me to another flight on CX to HK.
The risk with Scoot would be simply they have less flight between SG and the destinations, because they are running on a 300 seater plane while Jetstar runs on a 180 seater plane (both are estimates). Scoot normally flies once or at most twice a day to their destinations. If the plane is delayed or having a technical fault, you are screwed. So you must be prepared to be screwed either with insurance or buffer time.
When I went to HK/TW at the end of 2013, I fly Jetstar to HK and stay there 2 nights before flying to TW on a Cathay Pacific. If I transit on the same day to TW and my Jetstar delay, rebooking and worse missing an important event (this time my friend's wedding), too risky.
Users must know what they are into by booking budget, else you stand to be unhappy because you pay peanuts happily and think you will get Emperor's treatment, in the end make yourself a fool like those 22 or 23 on Scoot last year.