Have you asked any big time breeders this?
I didn't think so...............because if you had, you wouldn't have posted what you did.
Just so everyone is clear on this, some breeders cohabitate snakes. Period. Some of you who know no better can flap your gums all day that they don't, but that doesn't change the fact that they do. Some species breed easier if kept as pairs.
As for sick snakes - most breeders keep them in rack systems in which snakes are housed together in little tubs mere inches from each other.
Sickness will easily spread in rack systems and snake rooms even if *gasp* the animals are housed separately. Many viruses and some of the more aggressive bacteria don't respect a 1/4" of chinese plastic.
Only proper quarantine and veterinary examinations prevent the spread of most ophidian pathogens. After that, you can put them in the same room or tub together.
As for cannibalism - there is a difference between snakes that are truly ophiophagus and stupid bone-headed feeding mistakes that result in the accidental ingestion of a tank/tub mate.
Ball pythons are not naturally ophiophagus. But if a keeper is too ignorant to properly separate tank mates before feeding, then there is definitely an increased risk that one roommate may accidentally eat the other. Again, like the big "they'll both get sick if you house them together!" bugaboo, this is a risk than can be completely mitigated if the keeper utilizes an iota of common sense.
So when people claim ball pythons are cannibalistic - it's really a crock of crap. Balls have been known to eat other balls in rare (yes rare) instances where the keeper was too inexperienced to know better than to separate them at supper time.
Here's the cookie-cutter bit of advice to the OP - don't keep your snakes together. Not because it can't be done or isn't done successfully, but because it requires elevated husbandry skills, added care and added vigilance - most of which can't be imparted on a reptile forum.