I think it depends on your uses of your tractor. My backhoe also provided that
ballast but when I was out using the back blade with my bucket off, loader frame still on and my homemade plow on the front of my 75lbs forklift frame. Once the back blade hit the ground I had no extra weight for traction. wasn't like the back-blade gave that much more traction anyways.
I was thinking, one could weld up a frame out of rebar like the sub-frame of the backhoe a pour concrete around it. with a way to lift and attach and detach easily. could weigh 500 - 1000 lbs like the backhoe which would give you the best type of weight... the kind the comes off when you don't need it! You would still be able to use the 3 point for attachments and have the extra weight for pulling/pushing. Just a thought...