If it were mine, I would not slip pot it now. I would wait until after summer solstice and then do a real repot, complete with root work, moving it into the pond basket. That way roots can be corrected, sent on the right path, and then won't need more work for 2 to 4 or so years. If you only slip pot, the need to get started on root work will still be there, delaying the eventual move to a bonsai pot.
I am not sure how aggressive you should be with shoot removal if you do root work, but skipping shoot removal only looses one season, versus skipping root work which will delay root development by at least two years. If tree shows good vigor, you should be able to do something with shoots or bud selection or wiring this year.
Nice tree, I like it.