Outside Dry well

Older farm house. Foundation drainage and gray water both drain into an outdoor drywell. The drywell is about 12' deep and is accessed via a manhole cover. There is also a floor drain in the basement that connects to the well. At one time, there was a pedestal pump which stopped working and now we have a sump pump suspended in the well with a float switch. Water level gets too high, the pump turns on and discharges. The problem is if we loose power, the water backs up into the basement via the floor drain. There doesn't appear to be a way to install a backup system since you can only access from the top and it is so deep. The pump operates frequently with heavy rains combined with gray water usage from the house.

I've thought about rerouting the graywater drainage to my septic tank to elinimate that. Still have the foundation drainage. Of course, the pump always seems to fail in the middle of winter and I have to be outside changing the darn thing.

Any ideas about a backup system and how that could be installed? What about the idea of rerouting everything and installing a pit in the basement so I can easily access everything inside?