Essential MultiSite plugins for selling a service?

Hey there.

I'm just about to start building my first paid MultiSite service.

I'd like users to sign up for a monthly or annual subscription. If they fail to maintain their payments their website will go into a "grace" period before eventually showing a "please pay your bill" page. Each site will give the site owner the option of setting up their own custom domain.

Is someone more knowledgable able to confirm that I'll need the following multisite plugins and suggest any that are missing I should add:

* ProSites - setting up new sites automatically, subscription management

* Domain Mapping - allow users to select and map their own custom domain

* MultiSite Content Copier - automatically clone default content (pages, menus, page content, plugins etc) when a new paid site is purchased.

* Multi Domains - allow users without a custom domain to select from several base
domains

* Ultimate Branding - replace all core branding with our own Service branding.

Are there any other must use plugins that should be added to this list?

Are there any significant advantages to using WHMCS for deployment and billing vs straight ProSites?

Thanks in advance for your suggestions.

Kind regards,

Phill