From Single WP installation to Multi-Site Installation and SEO

OK, I have a small business customer that owns a number of keyword domains related to his industry. Our goal is take his existing Wordpress installation and create a multi-site installation with domain mapping and get each of those keyword domains indexed as individual sites.

Example: HVAC company ranked on first page of google for the keyword and location. However, we have 15 other domains like: HVACMichigan.com and HVACOhio.com and HVACIndiana.com. So rather than creating each of these into individual websites, our idea was to use the Multi-site functionality of Wordpress and the wpmedev plugins with domain mapping to get each of these domain names indexed individually.

So if you go to HVACMichigan.com you get one, (or more) pages that describe the Michigan services for google indexing purposes but all additional sites would provide linking back to the main website.

Has anyone done anything like this?

Is there a process that you'd recommend following to go from an existing Wordpress site to a Multi-site?

For the purposes of SEO, is there a better way of accomplishing what we're after and if not, are there any SEO and Google indexing ramifications of having a multi-site with domain mapping on the same IP address and the same control panel?

Thank you in advance, looking forward to your thoughts and experience with this.