That would take away the drama element, though. It's giving Data emotions, making Spock see there's more than just logic, letting Geordi stop having to use his eyebrows so much--all things that can happen in movies, but for a continuing show, it's too much of a game-changer. Let them be cured & it's just another appliance alien on the ship; YAWN. But...this diseased thing running the sickbay? Able to cure others & not itself? Dramatic irony by the tonne, son(ne). Puts a whole new spin on helping out random planets with their medical crises, too: they could either go the "WTF, WHY IS THERE A VIDIIAN HERE?! WHAT ARE YOU TRYING TO PULL?!?" route or the "I don't know what that is but HOLY SHIT IT'S UGLY WTF KEEP IT AWAY FROM ME" route.
I think it also brings up a great moral and ethical dilemma that's very real.
If a doctor is infected with a illness, should they still be allowed to practice?