Possible Image Onload Technique: How can I display a pop-up window to select criteria, that will then change the form data.

I'm sure that this can be dome natively.

I would use my not so patented User Focus technique to put the Customer in Focus for the current user.  The current user will be an entry in a self maintaining table of users.  The Focus Customer's checkboxes would be looked up into the User Focus record and then back down to the permitting requirement tabes where a formula checkbox would calculate which are relevant.  The button would refresh the record once clicked, and the embedded table of permitting requirements would show by form rule when the customer is in focus.

here are my cheat notes, but they are not step by step.

Edit or Create a User Record for the Current User (remember to set permissions in the User focus table)
Set Key Field
User Exists - true!

Remember to set permissions

var text AddUser = URLRoot() & "db/" & [_DBID_USER_FOCUS] & "?act=API_AddRecord"
 & "&_fid_6=" & ToText(User())
 & "&_fid_7=" & ToText([Record ID#]);

var text EditUser = URLRoot() & "db/" & [_DBID_USER_FOCUS] & "?act=API_EditRecord"
& "&key="  & ToText(User())
& "&_fid_7=" & ToText([Record ID#]);


var textIf([User exists?],
$EditUser, $AddUser);

"javascript:" &
"$.get('" & 
$URL & 
"',function(){" &
"location.reload(true);" &
"});" 
& "void(0);"



If you are good with formula URLs and relationships I can help you here, or else we would need to book 45 minutes on a GTM together to get this working for you.