Hi there! JoomlaCloner has this functionality already build in! You may notice in your 'View Backups' screen that there is a red mark(green means already published) for publishing the clone for frontend, that is used to share is to your users and let them install the clone automatically from the frontend!
In order to achieve what you want here are the steps you need to follow:
1. create the custom clone you want to share it with your users(i suggest you create a clean Joomla install, add your components and modules to include in backup)
2. go to your 'View Backups' screen and publish it for frontend(this step requires that you also configured the users clone path in your Configuration area, just under the full backup path)
Note: you may also transfer the clone to the service site and just use it there as a normal clone
3. Now you should see it in the frontend
http://mysiteurl.com?index.php=com_cloner or you can add a link to the component from your menu manager
4. Next, on that screen, all your users have to do is to select the clone(s), enter their ftp details and the install process will begin for them
Let me know on your questions!
Regards, Ovidiu