Alright here is my idea for a Witcher MUSH that focused mostly on Witchers.
The game would take place far enough into the future that current major characters have passed into legend/history, perhaps a 100 years or so. Because of the events of the Witcher 3 the world is plagued with a new wave of monsters that were released during the mini-Confluence of Spheres that happened during the finale of the Witcher 3. The current Witchers of the world managed for some time, but by the end of the century they came together to make a final decision, bring back the tradition of making new Witchers. But, they wanted to avoid mistakes that were made in the past.
First, all the Witcher schools were combined into a single school with many aspects, the school of the Chimera. All the facets of the various schools (Wolf, Griffon, Cat, Bear, Snake ect) are combined in this single school, and while there is now only one school, Witchers still specialize in specific aspects, so the factions of Wolf, Griffon, Cat, Bear, Snake still exist.
This combination of schools is mainly to avoid the history of the Cat, where Witchers of that school became glorified thugs and assassins, and fell off the Path. It also to divide the various powers of a Witcher. Witchers become much more specialized. With Wolf Witchers being excellent at tracking. Griffons at Sign mastery, Snakes with Alchemy. This would also generate the need for "squads" of Witchers to handle contracts.
By splitting the various powers the process to become a Witcher would also become a bit less strenuous with a slightly higher survival rate. (I actually have an idea for a plot line where a foreign King would approach the Witchers with demands to hand over the process to make Witchers, in hopes of creating super soldiers, ala Witcher 1)
Thus the game would be focused on the specific school in the contracts it handles, the inner politics of the various factions, and of course outside forces trying to influence the school.
Now its starting to sound like Harry Potter but with tits, swords, and monsters.... Hm.