If you're happy with XML, you might like to research XSL:FO, a schema for page layout which can be converted to PDF. Working with interactive tools is always going to be painful, and InDesign Server is probably overkill.
It is doable as XML. But I would look to using AI to create the graphs. For AI you can create scripts to automate much of the chart work, maybe all of it. The charting tool makes use of variables that can be loaded that contain the graph data and are XML files. Images are no issue if there need to be shots of units or people in the unit.
If you would like, I can upload a sample ZIP file that contains an ID CS6 file, two AI files that contain charts, two XML files for ID containing the text, and two variable files used to create the charts you'll see in the ID file. The screen shot below is using data from a sample poster PDF from a hospital I grabbed on-line, it's not mine. But for sample files I like to use more or less real data. The sample file is using roughly 1/3 of the sample PDF for its data.
Once it is opened--and likely relinked as your locations are not mine on the computer--you can highlight the Root in the XML panel, then import the second XML file and some of the data will be replaced (Successes is replaced with Failures, one of the chart keys and the chart itself). All this should be able to be scripted. In that once the XML data is pushed through AI and AI has (via the script) saved out the charts as numbered (or what ever scheme), then a script in ID could be written to load all the XML files, one at a time and produce a PDF for each unit.
Please note I do not have sample scripts for this process. However, there is a scripting forum you could ask for aid in if there are not scripts already available that could be modified for your purposes. I do this type of thing (sans using scripting) for a series of fliers for a large regional auto parts chain. All XML, but as there are only a max of 8 variations, I load the XML manually and produce the PDFs.
Anyway, just let me know if you want the sample data and I'll upload it and PM you a link to it.
Thank you for your quick and informative reply. Yes, if you could upload sample CS6 file that would be great! I'll spend some time looking at AI this week.
I greatly appreciate your help!