I agree that the maple has a certain charm, and I would not return it to the ground to fatten up the trunk. I would prune the top a little harder to let the bottom grow out. I think the pot is not quite wide enough, and could be not quite as deep. I think a wider and shallower pot would visually be a better match for the slender trunk. Also, I think the stand should be wider and not the same height as the pot. Maybe it isn't, but it sort of looks like it is on the picture.
I like growing my trees in pots. To return this tree to the ground for three or four years would ruin all the fine branching. A fat trunk isn't everything. However, if this tree was not as developed as it is, I might think differently.
Here is a maple of mine (A. palmatum 'Katsura'), that I bought as a cutting (about 5 years old at the time) in 1980 and have grown in a bonsai pot ever since. It is now about 80 cm tall with a trunk 8 cm wide at the base.
Reiner
