Maybe this would be a good exercise to start from scratch with purchased chromoly or aluminum tubing. This will heavy, but it will have the sidewall thicknesses to allow for TIG welding. As has stated many times in other threads, bicycle tubing is pretty exotic stuff that cannot be welded by just any ordinary (or even accomplished) welders.
So let them build their frames. I live in Michigan, and we have a tubing supplier here (I have a 10 foot long section of 6061 aluminum that has an OD of 2 inches in my garage that I bought from their scrap bin). I bet there is a tubing supplier in their town too. And there is always the Internet.
Some years back, some of my buddies built camping trailers that out perform a BOB using locally bought tubing.