I do not see the seriousness of it either Ascended. I don't do it but do believe it can be done in a way that can work. Many reptile exhibits do it without issue.
As to what jmcrook listed and many will agree with could not the same be considered for dogs.....or any other animal normally kept together? More than once I have found something in the backyard and wondered who it came from. All the listed things could happen with other animals yet many are housed together as normal care. Horses, rabbits, cows, chickens, dogs, and cats are some of the animals I had in multiples living together over the years.
If both snakes are healthy I just do not see the concern of one passing something to the other. Where did it get it? Where did it go or what did it get on its own that caused it? If the care is the same and provided by the same person all exposures should be the same. So why would one get sick and the other wouldn't?
I can see the hides, heat, and shade being an issue but think it could be overcome. My dogs like certain spots on the couch or a chair or wherever. If one gets there first they have another option that is providing the same level of comfort. Much like you can offer multiple locations of each for the snakes to all get what they need. This is why I don't go down this road though as it would require much larger enclosure than most can provide. That would be my argument against it. You will need double the enclosure to do it right, IMO.
So can it be done? I think so.
Should it be done? Probably not by a basic hobbyist.
But one that is advanced and willing to do what is really needed? Sure.
