You can manage this in several ways. The one you are trying is maybe not the easier. Normally the simples way is:
1-Organize group of 4 points (quads) from your list of lists of points of every level. You can find several custom nodes in the package manager related to quads. Anyway, I just uploaded Quads From Points Lists.
2-Define how to make the diagonal with a group of 4 points. You will manage the list of group of 4 points via transpose or with a custom function.