The 1917 GI barrel has a good deal of taper, reboring it to .375 or .416 would make it pretty thin and light. I don't know if it would be dangerously thin, but it would make up into a relatively light weight big magnum with a lot of kick and funny balance.
Also, a quality rebore would cost about as much as a new barrel; $425 at Clearwater. Or are you going to do the work yourself "I could safely rebore that barrel..."?
I have a few facts and a lot of opinions.