What do you want to get out of this tree?
It’s massive. Do you want a massive tree? I do, but maybe you do not. I don’t see a lot of great parts to air later off, but maybe they are indeed there. I think the trunk on the left has merit and I agree with @rafi that cutting back to the parts you want to keep is a good idea. I would not recommend putting this in the ground if you want a bonsai. This tree is already huge! Get a large pot, and reduce the roots a little more. Pot it up and let it grow for a year or two.
Ryan