Hi John,
So, what you are talking about is called Containment Information. Google says:
- Containment information indicating that your business is located inside another business (whether or not the businesses are part of the same organization).
- Not acceptable: "Chase ATM (in Duane Reade)", "Apple Store at Stanford Shopping Center", "Benefit Brow Bar - Bloomingdales", "Sam’s Club Tire & Battery (part of Sam’s Club)", "Geek Squad (inside Best Buy)"
- Acceptable: "Chase ATM", "Apple Store", "Benefit Brow Bar", "Sam’s Club Tire & Battery", "Geek Squad"
See the full guidelines here: https://support.google.com/business/answer/3038177?hl=en
Regarding your URLs, I would go with
Regarding keywords, this is tough because you are talking about so many locations. Typical advice looks like this
...but only if you have the resources to build a good, high quality page for each of the 1700 locations. If you do, I'd focus on service + city + regional terms and synonyms on the pages.
I might suggest, given the size of this client, that you hire a good Local SEO to consult with you, to whom you can show the actual business in confidence. The goal would be to have them confirm GMB eligibility, actually looking at your client. There can be nuances to that our community might miss, not looking at the actual business model. Investment in an hour or two of consulting with a top notch Local SEO would seem a wise investment to me, given the very big scope of the project. We have a list of trusted Local SEOs here: https://moz.com/learn/local/trusted-providers
Hope this helps!

