I dont think that is as big of an issue as you think, (though I dont think Im fully getting your image of "mainstreaming"?).
And I may, in my turn, have completely misunderstood what the OP envisioned.
Here's the crux of it: Why in the world are these supernaturals (Kobolds) working as "staff" in a public cafe/restaurant???
Brownies clean, it's just their nature. Cobbs make and repair shoes, and that's THEIR nature.
What kind of supernatural being waits tables, busses dirty dishes, does the barista bit, etc?
And keeps regular working hours?
In jobs that bring them into frequent contact with non-clued mortals?
In the Dresden'verse, I keep WTF'ing...
So it looks to me like they are trying to "mainstream:" trying to life a day-to-day life largely as if they were mortals themselves. Working and living alongside mortals. Passing as mortals.
Maybe that's just me, misunderstanding the OP ...