Would the garden hose retain a straight or slightly curved shape if you shot some expanding foam in one end? Not sure how far the foam would travel down the hose before turning solid but maybe you could do 18" or so sections of garden hose to get it to stay in its designed shape. Probably would need highest density expanding foam.
I love my Harbor Freight unibits for cutting into plastic. They blow through plastic so quickly and almost without effort. I think 1" may be the biggest they sell.
