Simplification: Use "thunar_tree_view_model" as well for icon view
Currently, we use two different models for the main view, one for list-view (thunar_tree_view_model) and for icon-view/compact-view (thunar_list_view_model) (Yes, the naming is awful)
Both have the purpose to manage the file-list in the view widget, while tree_view_model is more complex, because sub-folders are expandable. So actually one does a subset of the other.
Actually, it is rather simple to use thunar_tree_view_model as well for icon/compact view, so that thunar_list_view_model is not needed any more at all. Here a very incomplete patch: 0001-use-tree-view-model-for-icon-view.patch
Currently, exo checks GTK_TREE_MODEL_LIST_ONLY, which actually should not be of interest to exo, so the patch fakes that.
It looks like there is a problem with loading subfolders, so some more investigation is required, though in principle, it should work fine, boost performance (usage of hashtables) and remove ~2600 lines of duplicated code.