The solution for idolized chars in Ncr is easy, no bonus to karma for leaving raider faction (or vault city or bos faction, only penality because wasteland are harsh)
easy done
There's already a solution: Izolized/Liked reputation doesn't allow to you to shoot simply anyone, after 1st attack you'll lose protection and 100 reputation, so anyone can shoot you. If you die or be offline few hours you'll become protected again, but if you'll attack someone you'll lose 100 rep again, so you can keep only Liked status so long as you want, while for Idolized you'll need to make reputation-alts, who'll be in 3 factions one by one and with barter skill tagged, and when he'll never become Idolized again, you can make ~deleteself to him.
So, just kill that Idolized guy and he'll have problems. Btw it's very interesting and making character's life more valuable than items, forcing you to use edges of map and shooting people at the back when they don't see you.