Yes, what you suggest can indeed be done. Also, one can take the hose and completely wash away old potting medium, trim the roots, and repot in fresh stuff.

Incidentally, I used to have quite a collection of plants that grew large and needed bringing in each winter. It just finally got to be way too much work, and I've moved on to other pastimes! Good luck.

Look up online root pruning of potted plants.

It is sort of like bonsai in a way, trying to get a tree to grow smaller than it ever would. You can do that, in fact, you really have to do that, but it is ALOT of work to do it. Remove it from the exsisting pot it is in, wash the entire plant and roots off with the hose until it is naked of all soil. Now you can see the roots clearly.

Cut the roots at least by a third off the bottom of the tree. Then replant in fresh potting soil, your soil has depleted also.

You can also use Quick Start from Miracle Grow to stimulate the roots you have cut. It helps the plant. Keep the tree in a shaded area until it looks better, and then in a few weeks, gradually expose it to sunshine again.

I use to do that for a couple trees, and it works. It just is a lot of work, you really should be doing that every year or two, or it will decline again.

I trimmed it up today so we'll see how it goes! It was WAY rootbound like I expected and I did the bottom third. Wasn't a clear cut of all the roots, but I raked them out and it should give it additional room it needs to expand. Here's hoping!