Is it possible? Snakes are really just a minor nuisance now that scare your horse a bit. When they bite you it is really not an issue as you just drink a tonic and your fine. Snake bites are already so rare I would think that if you do get bit that it should be more serious.

 

Could it be modded that Snake bites can only be cured by going to the doctor? This would make doctors more useful as well since I never really need to go there. 

Could it be modded so that snake bites will kill you over time if you don't go to the doctor? Not sure what the timer for this should be, maybe 10 minutes or so.

find what causes their damage amounts and raise it.