From what I understand of the rules, you only need to provide one solvent tenant, i.e. someone who can afford the apartment. You don't have to do a search far and wide for 50 people and find the next great renter. If the landlord rejects that person for any reason other than not being able to pay, I think you're off the hook.

It's unlikely you'll have trouble finding someone in Lausanne to take over your lease terms. Just make sure that the candidates you put forward can cover it financially and have a valid permit.

Someone else probably has links to the relevant statutes that can back up the "only one solvent candidate" language.

@Gravity - No, deregistering and departing Switzerland doesn't relieve you of any and all financial obligatons including rent. You can use deregistration to get out of phone contracts and gym memberships often with cancellation penalties, but it doesn't get you out of a lease.