The concept is interesting, but the viability very much depends on the tone of the campaign you're in.
According to the novels, the Butters the ME and sometimes doctor to Harry was the person who examined the remains after a Harry-caused building fire at the end of Grave Peril. From the comment (made in Dead Beat I believe), Butters reported that some of the remains he examined were humanoid, but not human. He then spent somewhere between three and six months (depends on which novel you read...) involuntarily undergoing evaluation in a psychiatric ward.
Side note; In order for the Involuntary admission of Butters for three to six months to have been legal, within the 72 hours prior to his having been admitted a qualified physician, examiner or psychiatrist had to certify that he met the criteria for involuntary admission and hospitalization, meaning that he has mental issues which made him an immediate danger to himself or others. Further, within 24 hours of his having been admitted a different qualified mental health professional would also need to certify the he needed involuntary admission and hospitalization, again with the requirement that he was a danger to himself or others and that within 24 hours (not including weekends or holidays) of the second certification the facility/facility director would need file the certifications with the court. Within 5 days (again not including weekends and holidays) the court would need to have held a competency hearing for Butters before a judge, with an attorney for Butters. Again, one of the key parts is that the patient (Butters in this instance) needs to be a danger to themselves or others. You can be completely crazy, but as long as you're harmless you can't be held and treated involuntarily without breaking a number of laws and medical ethics.
In short, for Butters to have been held as long as he was without his consent, there were a number of people involved and either breaking the law by ignoring the required due process, or stating that Butters was a danger to himself or others.
Sorry for the long bit above, but I wanted to properly 'frame the scene' as it were within the Dresdenverse according to Jim. Basically the supernatural powers are very interested in keeping the 'mundanes' ignorant that the supernatural world is real and exists side by side with the 'real' world. Mortal authorities (who might be aware of the supernatural, or could be completely ignorant as well) are going to treat, literally, people who spout off about the supernatural in everyones's midst, like they are crazy and dangerous.
On the supernatural side, and also possibly on the clued-in mortal authority side, there is the distinct possibility that a 'hit' or even multiple 'hits' could be ordered on someone who became too much of a nuisance or was attracting too much mundane attention.
Susan, when she worked for the Midwest Arcane, basically appeared to be safe because the Midwest Arcane was considered a 'tabloid' publication, not unlike the old National Inquirer which would report people seeing demonic faces in storm clouds, unicorn and bigfoot sightings, Elvis with aliens, etc. Not the sort of publication people would ever take seriously.
Now, if the setting you're playing in or planning on running has room for someone trying to peel back the veil over mundane eyes, by all means go for it. It wouldn't work for long in the campaign I'm in, simply because eventually the character would become an inconvenience or obstacle for one or more of the supernatural groups and the character would get taken out. Whether it would be Fix being sent in by the Seelie Court to err, 'fix' things, or the Nickelheads drafting a new member, someone would end up getting to the character.
Also in the campaign itself, the storyteller has setup an NPC who is a reporter on the supernatural for the "New England Parapsychology Gazette" which is basically supposed to be a 'rag' publication like the Midwest Arcane, but focused on New England instead. The NPC is intended to be used to report on some of the supernatural events going on in the background of the campaign, as well as report on some of the events the players get involved in.
The write-up which has been posted so far (campaign started Oct. 22nd) is located here:
http://www.epicwords.com/entries/8337Now this particular reporter isn't a Pure Mortal. Instead he's an investigate reporter and closet Minor Talent with the supernatural power Supernatural Senses: covering a Nose for the Truth, a Nose for the Supernatural, and a Nose for Traces of the Supernatural. The reporter can literally smell when he's being lied to, when the supernatural is present, or when the supernatural had been present. Unfortunately for the reporter, he doesn't know that he has those supernatural powers...
-Cheers
Edit, additional comment: For those interested, the Illinois statues which dictate the requirements and processes for involuntary admission and hospitalization for mental health issues can be found at the link below.
http://www.ilga.gov/legislation/ilcs/ilcs4.asp?DocName=040500050HCh.+III+Art.+VI&ActID=1496&ChapterID=34&SeqStart=11400000&SeqEnd=12900000