Is it possible to convert a 5 on 5.5 9" axle shaft to 5 on 4.5? If so who can do it?

I don't have the funds for a front hub conversion in addition to my rear 9" swap.

I don't think I really want to use the conversion spacers, would rather have the shafts the right pattern.

What about the backing plates, can those be redrilled, and used safely and functionally?

You should be able to have them redrilled, or just have a new pair of axles made with that pattern, and then redrill your rotors to match. I've did this on my 8.8, but going in the opposite direction you're trying to go.

Now I'm competent and skilled enough to do an axle swap, and have done everything else but tire mounting and gear setup to the jeep.....so is redrilling the back plates a fine art, or as simple has measuring 5 holes and drilling?

That would be a fine art. If you misalign the holes the drum/rotor won't fit and it won't spin in a perfect circle. You will get vibes, shakes and possibly cause damage.

hopefully the hole in the axle that you use to access the bolts that hold the axle in place dosen't mess up the redrilling to 5 on 4.5