I have seen something similar to what you are asking, but it was for a 3-pt hitch mounted implement. I assume you want to store the backhoe in a relatively compact area so ideally you'd keep the stabilizers retracted. What I would do is create a T-shaped base with 3 caster wheels. Place one wheel under each of the stabilizer pivot points and one wheel under the bucket. Make this T out of something stout enough to avoid twisting, but light enough to be lifted. I'm thinking 2x4 rectangular steel with 11ga walls. Remember, it's only going to transfer 700 lbs directly to wheels so there just doesn't need to be an insane amount of strength. Under each stabilizer, weld a cheap jack stand directly to the T. You might need to add a bit of a platform to support this. Depending on clearance, you might need to do a drop-leg for the swiveling casters. That's really easy to do with rectangular tubing. Use swiveling casters like this:
http://www.homedepot.com/p/Richelie...ber-Swivel-Caster-with-Brake-F24804/204695849
Once it's all built, you would lower the bucket onto the single leg, raise the jack stands up to support under the stabilizers, and disconnect the backhoe. The stabilizers should still be able to pivot while the jacks are in place so they can be used to install/uninstall the backhoe directly to and from the tractor.