Found out the hard way the screw was titanium. An hour with a Dremel diamond burr bit and I had the head off the screw and the water bottle frame off. After that, it took a matter of minutes to grind off the Rivnut lip and punch the remnants into the frame.
I then discovered Litespeed uses a smaller Rivnut than Trek, Specialized, and Cannondale. Three days and $10 later, I now have two new ones and a couple spares. Now I need to find the time to install them.

Hillrider:2005 Litespeed Solano frame-set I found on Craigslist.

I will have to remember the hose clamp trick if this happens again