I liked your idea, and I am now attempting to get it to work, using the idea of populating the checkbox control fields with information from a sharepoint list. Since the time of that post, I've made some progress towards the goal.
I've run into some issues and I thought since they appeared to be data connection related, I should discuss it in another area of the forum - I apologize if that is bad ettiquette.
The first gotcha I encountered was that InfoPath's data connection wizard would not display a column if I had it defined as a people or group type column that allowed multiple people to be selected. I spent most of the morning fussing with that. It turns out if I change the column to only allow one person or group, then I can select it for the data connection. I still don't have a solution for that issue, because I have to allow multiple people to be selected.
Once I could get the data connector set up properly, then I set the first of the checkboxes up so that it was type text, had blank for unchecked, a dummy default (required by the control property). Then in the Submit button, I added a rule that indicated that if the field was not blank, the value of the field should be changed to a column in the data connection, using a search in the list to pick the specific row.
Then I created a second rule that concatenates the values of the checkboxes into a text field which I plan on using within an email data connection.
Seems like it should all work. However, when I do a preview, what I am seeing is that when the field value is set, the checkbox is visually being unset. The submit rule is concatenating the new value as expected. But visually, the checkbox appears to be unchecked.
Since my goal for the next step is to email the form to a couple of people, I have some concern that the form that will be mailed is going to continue to display the box unchecked. If that indeed happens, then I'm stuck, because the whole purpose of the process is to send this form correctly in two different emails.
Anyways, I surely appreciate the example form you posted yesterday. I've never seen an example doing things like that, so it opened a new area up to me. Thank you so much.