Clawed, we have knowledgeable tree experts on this site who could give you the specifics about why planting anything with a trunk in that condition is a bad idea and maybe they'll weigh in. I'm just a lowly dirt gardener who recognizes trouble waiting to happen when I see it. That split is an invitation to disease, insects, rot and instability. The problems might not manifest for a while, which is actually worse than immediate issues, because by then you've got a large, ailing established vine to deal with.
As to your original question about suggestions for repair, I have none. Usually a bark wound higher up will repair itself, but below the soil line in moisture seems mighty risky, no matter how resilient wisteria might be.
Perhaps you can show that photo to a local knowledgeable nursery person? Maybe someone like
@ViburnumValley might have better suggestions.
