You wouldn't need suspension to get height out of your box, just block it up off your axle with a steel frame to the desired height. As for the hitch I wouldn't put any holes in your bucket, I would weld a piece of steel across the top of the bucket to strengthen it up then weld or bolt the hitch to the top center of the bucket, bolt it somehow if you want to be able to take it off for general bucket use. Another option would be to fab up a mount for your hitch which would quick couple onto the loader in place of the bucket but then you would probably want to change it out to use the bucket to level your dirt and it would be more messin around welding. At work we have pintles on backhoe buckets and move trailers around that way all the time, they push backwards rather easily as you are moving slowly enough, the only problem you may have is if u make to trailer too short it may like to jackknife but at the speeds u will be moving I wouldn't worry about it.
That seems like good thinking `dawg. At the speed I'd be traveling w/it there shouldn't be a need for it. The fewer moving parts the better. Swick1 I'd planed to use good sized tires on it for the ground clearance.
Ron