me personally, I would want stronger axles and wider between the fenders...mines 83" and I wish it were wider at times.
The axles, I would look at possibly two 5K axle, atleast one with brakes. The reason being is if you are rated for 7K lbs. and you know your tractor weighs 6K...that only leaves 1K for the weight of the trailer (most trailers weigh 1500 or more)...to me thats cutting it close. It would only be a matter of time before you end up replacing the axles for more HD ones. As XJ_punk said, the price to go from 7K to 10K is quite a bit but, as I have pointed out, worth it.
The next trailer I buy/build will be 83" between fenders, minimum 2-3500 lb. axles, and fenders that can be driven on (walking on fenders bends them pretty badly too
). I would like the frame to be tube instead of channel or angle, a nice bulldog hitch, a nice HD Jack (similar to the semi style jacks), and ofcourse plenty of tie-downs all around the trailer. The down side is I just described probably close to a $5K trailer.