Budget is not a real concern & so having unique content would not be an issue either, since there is an on-staff writer & if required additional writers can be hired by the firm
The difficulty, IMO, is not getting unique prose, but rather getting unique ideas to express.
That said, good law sites, IMO, almost need to be content heavy...
for each type of offense or litigation, to prepare potential clients for the hurdles that they face, what information and documentation they'll need to gather, likely outcomes, etc.
Something important to be considered is naming conventions for the firm... Are there a few senior partners for whom the entire firm with its many offices is named... or is each office named for its senior partners (as in the classic "Dewey, Cheatem & Howe")? In either case, how are you going to distinguish between the names of the lawyers themselves and the name of the firm (or office)? Schema might be important for these distinctions.
My experience in geo targeting is that for this type of business, state names are unlikely to be used in "attorney placename" type queries. The articles that attract backlinks need to be useful guides for your potential clients, and these may or may not require jurisdiction names (ie, state, county, or city). You might do better to have a core site covering the basic principles of the law, perhaps referring to more local variations where necessary within the overview articles. I wouldn't try to have separate overview articles, though, for each locality. Google has gotten good at digging placenames out of a well-organized page, at least for long queries, which is how I'm increasingly finding myself searching.
I'd then use either placename subdomains or directories to cover the individual lawyers, testimonials, office location, etc. I myself would have one for each office. I think there's a much better chance for higher quality content this way, and fewer problems with article backlinks.
For best results, each location is going to have to attract a chunk of its own backlinks. You're going to have to be careful to avoid overlapping backlinks, btw, to the subdomains/directories in this part of your setup, if you "build" backlinks.
Natural backlinks usually sort this out by themselves. .
Hoping this is helpful.