Alexb2000
En-Route
4wd makes up for a lot of weight issues, but you make a good point. Tractors aren't just about pulling and pushing, they're about getting pushed. Once those 2 big tires lose grip, you've got a real situation on your hands. You haven't really had your life pass before your eyes until you get pushed down a hill by a running baler followed by a loaded hay wagon.
Maybe we haven't mentioned this specifically, but the OP should think about tires some. Home owners usually choose turf if they want to make it a big lawn mower out of the tractor. If the machine is going to be doing field work then he might need Ag's. Otherwise industrials will wear a lot better on hard pack.
As you said above traction is critical in many situations.