I have an eight seater Toyota with a 2 litre engine. It's not very economical but is sure is spacious. You can fit eight adults in it comfortably and there is space for luggage behind the seats.
Air con, electric windows, sunroof in the back, power steering, seats fold down to use as a bed or to load up like a van. Pretty brilliant really but ugly.
I used to have a car and a van. My people carrier can't replace a Transit van but it can fit most flat packs and other bulky items. I can get a lot more stuff in it than I could get in an estate car.
Like the others mention there might not be any fuel economy to be made with a smaller engine. My 2 litre engine is working hard uphill when fully loaded and a smaller engine unless it is turbo charged would be struggling.
I did have a 1.6 litre diesel estate car a few years back and it wasn't very economical, it really struggled uphill but it was great on the motorway.