Your existing stand where you simply lift the machine and put the pivot in the bottom hole is the simplest way to achieve having the machine on end. I don't think it needs to be in that position often anyway.
If you want all positions without taking the machine off the stand I would do it like this:
You can build the stand out of wood too. Use plywood for the rings.
I draw terribly. Keep the outer part of your existing stand the same. Instead of the large outer ring use a smaller flat ring as the sewing machine base. Add 2 wide pads (or another ring to rest the base ring on) with clamps at the bottom of your verticals. In the horizontal position in your drawing above you would be able to spin the machine so the ends face you and you can tilt the machine on either end by rotating the ring.
Or like this:
If you have access to metal working tools you can make your base like an engine stand too. For reference:
http://www.harborfreight.com/catalog...q=engine+stand
That would give you easy access to 3 sides and the top and bottom. The metal mounting bracket and pivot would have to be heavier so it doesn't flex. If you hinge the main upright you can turn the machine vertically too. You would need either a wider base, a counterweight, or need to bolt it down for stability though.
The big thing is the idea. Your idea to build a work stand is brilliant. There's a lot of ways to build it once you have the idea.
Rodney