All true... and personally I have done a lot of wheel modifications, too. But I do laser-cutting /welding /grinding on the lathe, in a way that you couldn't tell where the joint is. (And the finished product has zero runout, unlike what comes from factory...)
What you have in mind goes a bit further than just "lip-reinforcing"...
Have you actually measured a 17" rim? I guess, not. The OA diameter is a tad over 18.5", while the HMMWV rim measures 17-7/16". So a 1/4" rod all around won't do it, obviously. Then you seem to forget the fact that the 17" is a 5deg shoulder rim, while the 16.5 has 15⁰. How would you address that? Fill up with bondo - I hope not...!?
Here are both, face-to-face, for comparison:
View attachment 804973 View attachment 804974
Building a (safe!) 17" bolt-together wheel (that could hardly be distinguished from a stock HMMWV wheel, once mounted) is possible and not so difficult. But as I said above, you need to have the 17" rims to serve as donors for the bead sections. And then it's only a matter of cut & (MIG)weld-together.
I'm on the wrong side of the world and too far away to offer the final product or even a prototype, but I could gladly assist you with some to-scale drawings, if it came that far.