Is there a way to have a ListCtrl cell span several columns? Or perhaps to able to append a panel / other element to a ListCtrl item that will contain the info I need?
No. The ListCtrl does not support that functionality. There is a pure Python list control widget called the UltimateListCtrl that allows you add any widget to a cell, although it doesn't appear to allow cell spanning either. I would still try this widget and see if it works for you. If it does not, you may be able to patch it yourself because it's written in Python or you could do a feature request for it to be added to the UltimateListCtrl on the wxPython mailing list and see if anyone takes you up on it.
You can do spanning in a wx.Grid widget if you wanted to go that route, although it's pretty limited when it comes to embedding other widgets.
Possible for ListCtrl Colspan, or similar functionality?