I am curious why no enterprising gun maker/entrepreneur has decided to offer extra barrel sets for popular makes, i.e., Parker, Fox, Smith, Lefever, etc.  I realize there is hand-fitting involved with each one, but that is what smiths are for, and I'm sure they would appreciate the extra business.
Who wouldn't want an extra barrel set in a different configuration  for their favorite sxs?  I believe many would prefer to go that route than to buy another gun.  It just seems like a no brainer to me.  No doubt it would be expensive, and require a lot of different tooling, etc., but no worthwhile business venture is ever easy.