WHMCS, Blog Templates, Pro Site workflow

I am trying to automate the creation of a site within a multisite environment, using WHMCS Provisioning, Pro Sites, Blog Templates and Cloner.

Our ideal workflow would be; user signs up, chooses domain, hosting (Pro Site plugin), theme template (Blog Templates plugin), and pays at WHMCS. Site is then created at http://sub.domain.com and pre-configured with selected template. (No need for Cloner)

Now I know this workflow is achievable if purchased through the WP site but from what I can gather the WHMCS/WP integration via the Provisioning plugin is only one way; WHMCS to WP, we also need our customers to manage their details at the WHMCS side for consistency.

So I'm considering the following, alternative, workflow:
User signs up & pays for site/hosting/domain on WHMCS.
The new site is created automatically at http://sub.domain.com which is preconfigured using the default theme option in Blog Templates.
The newly created site is essentially an options page, listing all available themes/blog templates.
User logins selects the required theme/template which triggers the Cloner plugin to clone the site selected and replace the current theme/template on their site.

The first problem I see is around permissions I think; as the user is only a site admin they do not have the privileges to clone sites? The next would be preventing the user from selecting a theme/template they are not entitled to use. And thirdly I'm not sure how I would trigger the cloning element of this workflow?

Any help or advise would be greatly appreciated.