Yes that is one option I’ve thought about, even asked about it in tree buying forum. Going to be really hard to find a small tree with this sort of age on it and the type of twisty elements to match up with what is there. But I do like that idea as well.
You only need to look within the tree itself. I see one or two twisty branches that could be layered off and planted into the root base strategically, to form the 5th trunk, albeit much thinner than the rest, thats ok though, it can be set to come from the rear to offer more depth.
Im developing this Beech clump, the two side trunks have been taken from the mother/central tree. They've been planted into little gaps I found in the base of the mother tree, roots should entwine/fuse over time, become one root pad. Ive done this with Pommegranate too
Couldn’t find one that seemed like the right fit this year. I did get a long narrow rectangle unglazed I like but tree needs to grow a little more for a good fit for that one.