It will essentially work, what you have drawn up. There is no need really for a cutoff valve on the drain, so long as the inlet is high enough up in the tank. If your pump fails, nothing will happen, except the drain will run until it can't get any more water. So long as you always leave room in the sump to handle whatever water drains when the pump is off, you will be fine. The inlet for the drain for that reason needs to be near the top of the tank. This is often done with a durso standpipe, and an acrylic overflow. You also want to make sure you have a small hole in our return pipe that is above the water so that if you do lose the pump, you don't siphon water back out of the tank through the outlet. A small hole above the waterline will break the siphon.
Also you want to make sure your return pump is sized such that the drain will always be faster than what the return pump can return.