I have not, but walls and roofs can handle slopes no problem. Roof slopes by including the roof slope arrow when constructing the boundaries of the diaphragm. The tops and bottoms of walls can be attached to sloped reference planes, no problem. But as you are already aware of, the structural footings do not respond well when the bottom of the wall is sloped. It's a rough work around, and not knowing the extent of what you're modeling and how detailed you need it to be, but in a pinch I suppose you could always use the same reference planes used to slope the bottom of the wall to provide the slope for some concrete beams that represent the footings. Admittedly it's not the most "revitty" solution, but if you're pressed for time. The structural footings are out of the box families for Revit, so I'm not sure if you can tweak the family such that the top of the footings acknowledge the bottom of a sloped wall. Hope this helps.
