What type of sewage ejector system would you recommend.

[Bird Doo Head]

Will it work out to have the pump pit indoors using one that comes with a gas tight lid & proper venting? Then pump freezing isn't a problem.

The toilets with built in pumps won't freeze.

I don't know if hoarfrost will build in the pipe underground and block it. You may have to bury the pipe below the frost line if you get prolonged times of below freeing weather.