@Stratosfear The RhinoReverse patch looks great(!) From what I can see it looks super-smooth. I wish it wasn't $1290 USD! Based on the intended purpose I'd mostly just use only the patch function. I think I'd feel I'd have to make everything out of patches to justify the cost
For the light lines/ zebra stripes, no you're not wrong at least for what I made in the video which was a relatively quick version (doing it manually just isn't fast, period). But with a bit of practice and little bit of manual tweaking, I've been able to get it pretty close:
cornerBlend7.3dm (234.4 KB)
The light lines/ zebra lines aren't perfect (especially in the very centre of the corner), but it's not bad. The three surfaces meeting in the corner do not have G2 continuity. My goal is always to use the least number of control points and single span surfaces where possible. In this case I did not achieve this but the results are pretty o.k. considering there are no extra plugins needed. And all the blend surfaces are untrimmed. It's taken me a while to figure out how to get it working fairly consistently. The devil is in the details and one needs to understand the underlying continuity issues and play around with the software for a while to figure it out. I don't think there is a magic workflow solution for this problem, but a decent theoretical understanding of continuity issues doesn't hurt.
As much as possible, pre-planning the topology helps (or at least not painting one's self into a corner, like what Jason said about compromising). The problem with trying to find a good solution to the problem posed in the video is that one is starting with a trimmed edge(s). It's not a good starting place. A bit like fillets, if at all possible I like to leave trims until last or avoid them altogether because it just adds spans/ control points and can make the surfaces unnecessarily complex. Using the patch solution isn't ideal topolgically and it's blending a trimmed surface with another trimmed surface. It's not so bad if it's the final modeling step, but if the surface requires further work, it could create problems.
I agree with you that it would be ideal if there was a native software solution that could solve setback fillets with untrimmed surfaces while maintaining G2 continuity. At the moment I don't think there's an [obvious] ideal, native solution in Rhino to this modeling problem. Being relatively new to Rhino, the whole process of figuring out how to do it manually really helped my understanding of maintaining continuity (which is why I bothered, I started learning Rhino in February), but I won't use the manual method very often in a production setting (it's just not time/ cost effective).
I would bet that coding a solution to this issue isn't exactly straightforward. I'll keep my fingers crossed that it ends up on the task list along with some of the other things on my wishlist.