Champions should have a loyalty rating that determines 1) their chance of remaining with their sovereign if the sovereign slays a neutral champion and 2) the chance of a sovereign recruiting the champion if the sovereign has slain a neutral champion.
This would force players to weigh the pros and cons of an early game champion slaying campaign and differentiate champions from one another.
Example: Retaining a Champion
Champion Jakor, the merchant - Loyalty Rating: 25 - If his sovereign slays a neutral adventurer there is a 75% this champion will leave the service of his sovereign.
Champion Mytal - Loyalty Rating: 100 - If his sovereign slays a neutral adventurer there is a 0% that his champion will leave his sovereign's service.
Champion Zardoz - Loyalty Rating 70 - There is a 30% that this champion will not offer his services to a sovereign that slew a neutral champion.