The following screenshots are of the basic design and principles for creating this. The RSNOR latch and track layouts can be easily adjusted to save space or add functionality. I also do not include an arrival track onto the switching point, but a track can be run to a couple blocks above and drop a cart (and rider) onto the powered track piece (or any other number of ways to put a cart into place).
And the screenshots with explanations (click for larger versions):
EDIT:
Also I don't want to claim to have invented this completely. I was inspired and this is sort of just a reworking of the following video:
