But considering that almost all of Butters' experience and knowledge is cutting up dead bodies, his skills are not very useful except to make assessments about how damaged another person is.
For instance, a very experienced, "high level" daycare worker won't be much good in a campaign either unless he or she has a minor talent or a massive amount of research into the supernatural.
If the campaign is going to be about how normal mortals cope with the supernatural, then ALL the players can be made at a low level. If one player is going to be higher level, then the challenges are going to be either too easy for that player, or too hard for the other players. DFRPG isn't the same as, say, Hero system or D&D, where challenge level is an almost mathematically determined, but there are still balance concepts at work.
Daycare workers and coroners are extreme examples of character concepts, and I wonder why they would be chosen in a Submerged-level game, without there being something else that makes them noteworthy. Butters was certainly a large part of the books he was in, but he can still be considered an NPC. Why are these character concepts on the table?
Murphy, Thomas, Michael, Kincaid: those are the general benchmarks in the game of the "Dresden Files" novels - the people Harry generally opts to have in his "party" when things hit the fan.
And if "daycare worker" or "clued-in coroner" are absolutely pivotal to each player's happy gaming experience, but they do not want supercharged versions of such professions, then those players can spend all of their Submerged-level skill points on having a greater number of skills at lower ranks, rather than aiming for higher skill points - for more of an "everyman" competency base. And buy very few Stunts.
And even then, they are still going to want those extra, unspent Refresh points so they get a greater number of Fate Points during a refresh period, which gives them a better chance of surviving the encounters their Submerged-level spellcaster friend is probably going to be getting them into.
Edit: in the Unisystem games "Buffy," "Angel" and "Army of Darkness," they did have a mechanism for balancing the powerful Lead types against the lower-level normal people, and one of those was to award the less powerful types more Drama Points (roughly equivalent to Action or Fate Points). Those less powerful archetypes could save up those Drama Points for other benefits, but at the end of the day,m they generally needed those in order to survive things that were challenging their Lead player, their Buffy, Angel, Ash (and in this case, Harry Dresden).
Also, I'm currently in a game where I play the "lead" spellcaster, with a mortal and a secret WCV Virgin in tow, and even though we are all at the same Refresh level, there is still a distinct perception that the mortal and the non-spellcaster have to work hard to contribute in a fight, though they outshine my spellcaster in the more social challenges. If the mortal player had opted to "downgrade" his abilities (he's playing a high school whiz kid), he would be feeling even less useful. So you don't have to hamstring one or two players in the name of believability. The game can be hard enough as it is.