"It's awesome and would totally make sense in Fusion. Plus I think it doesn't require a ton of development."
I won't disagree on the first point, but I will on the second. Yes, it would be great to have the ability to move edges. However, implementing this would be a huge investment. And, the main reason is in your description of MODO: "It's a modeling software meant for video games and films, not engineering". Fusion supports analytic geometry such as cylinders, planes, tori, etc. However, if we allow edge moving, you can see that those types of geometry could change their nature. Imagine twisting the edge of a box. That could potentially change the nature of planar surfaces on 4 sides of the box from planes to a curved surface (presumably NURBS or some other representation). I don't know anything about MODO, but I suspect that it (and other similar tools), represent all surfaces as NURBS (even planes and cylinders), which makes it pretty easy to make this type of edit (just changing some of the control points of the surface), while in Fusion, that is not so easy. There are benefits to keeping the analytic geometry definitions (precision, simplicity, performance), so we are not interested in getting rid of those. The current face-based edits, you will notice, do not change the basic definition of either the surface being edited, or adjacent faces.
If you haven't already, I suggest you check out the Form workspace, which does implement this kind of edit paradigm (you can edit any face, edge or vertex in the model).
Jeff Strater
Engineering Director