Thanks Tim, and everyone else that have made nice comments.
I have not planted other rootstock around the periphery for support, but I have many young branches pointing down from the top layer and up from the bottom layer and I may create grafts joining the two layers (not the branches end-to-end) for more rigid support and for aesthetics.
Each year has been a different experience with this tree, and I don't think I am done yet with its shaping and personalizing. It's never really done.
I really do encourage you Joyce to pick the four or five varieties you would like, or can get cuttings of, spend some time just staring at that tree, thinking about what you'd like it to be in five years, thin it drastically, and bark-graft your cuttings onto some of the stumps. It is the right time of year, or will be soon depending on where you are.
Start a thread with some pics of the tree and I'm sure you'll get some great feedback. THis has been a moderately challenging and greatly satisfying diversion for me, and I would share it with you! plus you get to post pics and receive praise from a bunch of weirdos!!
ETA: I thought it bore mentioning that, although I am here, now, and often, and I do post, and I undeniably do have an unhealthy obsession with gardening in general and my painstakingly-crafted fig tree in particular, I am most certainly not, unlike the rest of you freaks, I repeat, not, a fig weirdo.