timing of a replicator sequence

Sequence Replicator have a "Traversal" parameter. Setting it to Custom will present a "Location" parameter that can be keyframed to set a delay, then progress to any point in the animation you want it to stop.

Another way to go is to duplicate the Replicator and for one of the copies, set the in point at 0 (or 1, depending on your settings) and an out point at the end of the fade in. Start the second copy (the one with your Sequence Replicator animation) at the point you want the animation to start.

You can use the Fade-In/Out behavior for fades. Or keyframe opacity manually.

Motion's replicator isn't really a pre-set. What do you mean manipulate the timing? In what specific way? There are lots of parameters you can keyframe and replicator behaviors to use.