I have a weird question: do you think the Dresdenverse is set up to allow multiple (presumably regional) Knights for each Court?
One could go several ways with the Chicago-centric elements of the Dresden Files series:
1) Chicago is just that awesome, and the high amount of human potential and industry there translates to an analogous amount of supernatural activity
2) Dresden is there, Mab has it bad for Dresden, which means Winter is there all the time, which means Summer kinda gets roped into Chicago simply to preserve balance
3) Chicago is just one place: there are similar tinderboxes of supernatural activity all over the globe, and while the Fairy Courts are theoretically in all places at all times, the local supernatural status quo is going to look different depending on your locale
Yes, it could be allowed/balanced. The courts would need a little tweaking; they'd need to hae the same number of knights or fall out of balance.
For game purposes if you keep with cannon events you have some options:
1.Extra knights (maybe more like squires?)
2.Knights have a special mode of travel to let them counter the other courts, serve the court's intrests, and have a semblance of a life - all while being at Chicago when needed as well as everywhere else.
3. Chicago is that important to your game (you'll have to accept that the game will have NPC's from the novbels then
4. Chicago is infact only a small % of what is happening and the Knights are very busy elsewhere also...somehow they find the time.
Also, this allows PC's to play Knights of courts regardless of setting used.
It is your table, do what you need to do. I wouldn't have issue with it so long as the table I was playing at handled it with some forethought.