How about compensation for putting the pax through the scare not once but twice? I'm not sure about you, but I've never had two twice failed take-offs then forced to try the third time, but I would imagine it to be a scary if not traumatic experience. Like others might have mentioned, you trust the airline, and you trust the captain. But if the plane is simply not working after two tries, it is not just trust that is required here. Isn't there a saying that goes, fool me once, fool me twice....

And also, how about compensation for the delay in arrival, the worries the incident has caused the friends and families of those pax on board who awaits them on their destination? How about for missed connection? How about for those who specifically picked the flight or airline for the service and timing, ie, dinner then sleep till arrival? 3am take-off would likely translates into ~4am dinner service, which probably not what most pax had in mind when they booked a flight at midnight.

I know none of those things are listed in the contract of carriage as grounds for compensation. Personally I think it is unreasonable for the airilne to tell you they can't fly because of mechanical failure, and forced you to stay on the same plane and try again, then again, because letting you voluntarily leave would cause them too much trouble on top of the trouble they have. I think there might be a legal term for forcibly limiting a person's right to mobility to a confined space, and if there is one, then, well, definitely grounds for compensation, and if not, criminal lawsuits.

Legalities aside, there is also ethics involved. Even if CX can walk away 100% clean with no responsibility, some formal apologies for the pax's troubles would be the least they could offer. OT: JAL previously apologised more than once to its pax and frequent flyers for causing them worries about the future of JAL with its bankruptcy. Without being asked to, without having any contracts saying it needed to.
Now I think 2x failed take-offs with a plane full of pax on it is might be different cause for concern/worries than airline bankruptcy, which is why I think CX should provide some form of compensation without being requested, and if that is too much to cough up or just does not seem to justify the cost, how about a simple apology? It doesn't cost much, does it?