Are there Taxi wagons to carry 4 adults + 4 large luggages and 4 hand luggage, from beijing airport

I'm afraid there are no such taxis and if by normal taxi, you may need three. As I know, this website offers car rental service with drivers, you may contact them to see if they can help. Here is their contact info: booking@travelchinaguide.com
Hope helpful~

I can't believe, there are no hire cars or taxis that can carry 4 passengers & the luggage, from PEK Int. Airport to the city. Once when I arrived by a cruise ship, I found a wagon that could carry the same, from Tianjin to BJ. I have found such mode of transport in many places in the world, but a bit surprised that no such transport is available in BJ, in a time, when most of the things in the world are "Chinese". I am sure there is some one or a business that can advise me, ASAP. I don't hope to drive, while in China.

An official taxi in the city cannot hold you all indeed, but some larger cars and vans for rental are available at the airport. Except the way, I have a suggestion:
book a pick-up service from certain agency. I used the pick-up service of Travel China Guide anyway. They served well and the charge is reasonable. Here is their contact for your reference:
booking@travelchinaguide.com