I commuted on an '84 Le Tour for a year before it got wrecked. I replaced it with an LHT. I loved the ride of the Schwinn, but the LHT is definitely more stable under a load. Longer wheelbase and other geometry, I suppose.
On the '84, I had to mount the rack a little high and slide the panniers back to avoid heel strike, so that may have been a bit of an issue with the stablity. As a "sport" tourer, it was a little short in the chain stays. I got fenders on it, too, but it was tight. I stayed with 27-inch wheels because it had good sturdy Weinmann rims.
So it's doable, and definitely cheaper. It might work better if you can find a real touring frame, like a Voyageur, instead of the Le Tour.