Hello Bill,
Thanks for coming to Q&A with your question. The NAP is really the key, more so than the website. For the business to be able to treat each specialty as distinct, it would need to become 4 distinct companies, each with a unique legal business name, legit physical street address and local area code phone number. This scenario would enable the owner to have a unique Google Place Page for each of the businesses, instead of just one Place Page for all of his specialties (as well as having unique listings in all of the other local business indexes). As things currently are, he is permitted to have only the one listing per index.
This is the case for most businesses like that of your client and by building out his content on his website, you are doing pretty much what you can do for his organic campaign (plus linkbuilding, social media, video etc., of course).
The tough thing about clients like this one, is that they typically not only offer a menu of very varied services, but they also tend to serve in a number of surrounding cities. So an SEO/Local SEO campaign typically looks something like this:
1. Get the client listed in the major local indexes.
2. Campaign for reviews in a variety of sources.
3. Get citations for his Google Place Page
4. Build out a body of service-related content on the website.
5. Build out a body of geographic content on his website.
6. Build links every which way
7. Engage in additional forms of marketing that will be most effective at reaching the client's audience (email, video, social media, blogging, etc.)
Now, in entering into all of this work, the client must be informed up front that his chances of ranking above the fold of Google's results are mostly going to revolve around his services in his city of location, in that he may achieve grey pinned local results for these 'service + geo' terms. He may not be able to expect top rankings for all 4 services. In any service city where he isn't physically located, the client should be made to understand that he is most likely to have to rely solely on the organic rankings below the local results, as Google will be viewing his competitors with physical locations in those cities as most relevant.
Clients like these are more complicated than, for example, a dentist with an office in Denver. But, that being said, there are substantial benefits to engaging in the work. Even lower rankings for terms can lead to trickles of monthly traffic and if these convert to phone calls and bookings, it has all been worth it.
Good luck!