I came across this thread looking for exactly this behavior. Can’t quite understand why this isn’t already implemented in Adobe After Effects CC since it’s a hassle to have to move keyframes when retiming on different layers because their timing behavior can be considered “linked together”. (i.e. fading out when another layer fades in)
You can simplify many things by using null objects and linking properties (and layers), but linking multiple behaviors using markers would be a great way forward.