[@BlackSam3091] All of those concepts sound pretty interesting, I think the old shellshocked Witcher is probably the most compelling followed by the idea of an outcast Aen Elle. The guardsman idea is cool too, but I have a bias for oddball characters. 

For the veteran somewhat psycho Witcher, I think my younger newbie Witcher would be a good foil. He'd be new relatively with only a few years at most of Witcher experience, and is still largely idealistic and not jaded. Still finds satisfaction in protecting people and fulfilling contracts. He's also a bit of a maverick among other Witchers but largely because he tends to try and spare as many monsters as he can instead of killing them, and often gets involved in matters other Witchers might ignore such as bandit attacks. The young witcher hopes that with his efforts he can really change things for the better and show people that Witchers can be trusted. He's also the rumored bastard of some lord or knight. Perhaps he could chance upon this Veteran in the field and decide to team up to track down the mysterious monster, hoping that he can learn something from his older comrade. 

However I think another interesting companion to that Veteran would be a young Mage, well he's really 50 but he's young for a mage, who comes from a noble family and is smooth-talking and genteel. He's an ardent believer in scientific advancement and enlightenment but is also kind of arrogant and superior. Has a lot of power but not as much refined control and discipline as older sorcerers. Hates the leadership of the free city and hopes to change things to allow toleration of magic. Perhaps he's been one of the Veteran's few companions, accompanying him along to research the beasts he kills and help him with equipment, and persuades him to take the contract on the mysterious beast. 

For the Guardsman, I think an interesting foil might be a female elven thief. Young but skilled, and is slowly gaining enough money to buy her way out of the forsaken city. She is a relative newcomer but has never been caught and is making a reputation for herself as a skilled professional among the underworld. Has numerous contacts and even bribes a few guardsmen to stay inconspicuous and out of a cell. The guardsman might bumble his way into one of her heists and the guardsman decides to enlist her help in ferreting out leads on the monster by asking around in the city's seedy underbelly. 

A good companion for the banished elf might be another outsider. A female warrior with telekinetic powers, used to be a lord's daughter but left her home after being betrothed to a man she did not love. She isn't as strong as a mage or more experienced psionic, but has as much strength as a Witcher using a basic Aard sign and was training at swords since she was a child, to her father's disapproval. Now she's a travelling female knights errant who rights wrongs and tries to make an extra bit of cash taking jobs from merchants and lords. Perhaps the two can decide to partner up as sellswords and track down the monster for some money. 

Of course, the Young Witcher and my Mage idea could both be good foils for the Aen Elle as well depending. What do you think?

My young witcher and your conman werewolf could still be a great duo too.