You're right - that's really poor placement :-) And you never want to have to consistently prune a maple like this to keep it in size. It will never look very good.

I'd move it to a better location where it can be allowed to grow unchecked. Late winter or early spring just before it emerges from dormancy is ideal. If you have to, you can do it now, but I'd prefer to wait.

ps. It is considered more appropriate (and polite) to spell out 'Japanese' or abbreviate with just the initial 'J' only.

Moving it will take a good bit of elbow grease. You'll want to dig a fairly large hole around the tree(3' wide if you can) so that you take as many of the current roots with you as you can. It may suffer some from transplanting shock no matter what, but if you move it carefully and get it back into the ground this fall or winter you'll be OK.

Like other people said, late winter or early spring before the buds break is the best time to move.

But if you have time, a year prior to the move, following the drip line of the tree, use a flat blade shovel, create a ring as deep as possible to seperate the roots outside the ring. But leave the plant in place, this would allow the plant to heal, and send out new roots within the ring and also from avoiding too much shock when moved a year later..

Maple trees have shallow surface roots but can extend down 2 - 3', but dig as big of a root ball as possible to lessen shock.

good luck!. it is a beautiful tree!