The key element will remain the ownership of the file that will be incorrect.
When you will create the bridge between the cPanel account, the directory ownership and all the files will be owned by the other account and you will not have the access.

I can just tell you to try but I suspect that it will not work due to the permissinos.

The think that you perhaps should have to manage is the Server user and group permission.
If you put all the cPanel account in the same group and open the security for the group, perhaps you could manage different cPanel account that have access to another cPanel account.
So see if you could manage the linux user permission and groups.
Also see if you can modify the cPanel group management to allow create directory with the appropriate group of "cPanel".

My latest intent was to use the "slave site" cPanel accounts only to preserve the current IP addresses.

Recall that I was describing that all cPanel accounts would use documentroot of /home/jmsmaster/public_html where all files would have "master site" owner and group permissions.

All files would resides under /home/jmsmaster/public_html. File management would occur only via the "master site" cPanel account. And, public (permission) access via the web should be fine.

Sorry but I don't see how you can have several cPanel account with the same directory for all the cPanel account.
In general when you create a cPanel account, you have a directory like /home/XXXXXX/public_html where XXXX is the account.

So if you want to have the same "document root" for all the account I suspect that you have to directly modifying the apaches configuration files outside cPanel.

I read your jms2win_UsersManual_V120.pdf and it says...

Suppose you have a master website with the domain “www.master.com”
physically installed in the directory ‘/public_html/master’ and that you have
defined ‘slave 1’ with the domain “www.slave1.com”.
This means that you have to setup your environment to declare the
“www.slave1.com” that it is mapped to the same directory than the master
‘/public_html/master’.
The expected result is :
Website Domain Folder path
Master www.master.com /public_html/master
Slave1 www.slave1.com /public_html/master

3.2.4 How to configure httpd.conf with apache

In apache, you can configure the “httpd.conf” file to declare multiple
virtualhost entries pointing to the same directory.
<VirtualHost *>
ServerName domain_01.com
ServerAlias *. domain_01.com
DocumentRoot /var/www/html/php/MultiSites
User apache
Group apache
</VirtualHost>
<VirtualHost *>
ServerName domain_02.com
ServerAlias *. domain_02.com
DocumentRoot /var/www/html/php/MultiSites
User apache
Group apache
</VirtualHost>

If you are managing directly the apaches configuration files and not using cPanel with all its security, the answer is not the same.
As soon as you are using cPanel, you have plenty security added and managed by cPanel.

If you are not using cPanel then manage the file and folder ownership manually (outside of cPanel).
In this case, you also don't need of a cPanel to setup manually your virtual host with the IP that you want

Thanks for your answers and patience with my lack of knowledge. I'll work with my VPS provider to determine a workable configuration.

On a related topic, do you have any .htaccess migration suggestions or solutions to address the following?

1. RewriteCond %{HTTP_HOST} ^www\.domain\.com$ [NC]
RewriteRule (.*) domain.com/$1 [R=301,L]

2. RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*\.(js|css))$ folder/?$1

The first case is just a typical rewrite an incoming request to www.domain.com to domain.com. But, how does this work with JMS in place?

In the second case, a program in public_html/folder is being invoked under certain conditions. Same question. How might this work using JMS?

I'm assuming it works by using some conditional logic on the incoming HTTP_HOST instead of presuming we know the incoming domain. Do you happen to have any examples?

Thanks again!