"My one suggestion is that you be sure that both cities' pages are accessible from the top level navigation. You mention building a second site within the site."
By second site within the site, I simply meant that once you're at the "home page" for the second location, virtually all of the menu links and content are unique to that location. For example, the root page links to Services > Service 1 which is optimized for Initial Location Services. On the Second Location home, they'd be unique URLs/Pages and would not show the initial locations NAP in the footer or anything.
"I'm not completely sure of what you are envisioning here, but did want to mention that I think it's important that the pages for both city a and city b are accessible from the main menu."
We will definitely have a link to our additional location in the main menu. The home page is a functional WordPress layout for the initial city (which is in the domain name), the menu/homepage will have a link to the additional city (which is the same layout as the main homepage, but with a unique menu and NAP). I definitely plan on having the homepage link to our second location so we can piggyback on the authority/juice of home page.
Wesley,
Thanks for the detailed and informative post. The only thing I'd like to point out is that I'm not referring to building out pages for service areas (although we will do that for a few of them), but an additional "home page" within the site for a city we actually have a location in.
So basically it's quite a bit different than building doorway pages when it's a legit "home page" for our actual location.