Write & modify and design WHMCS - website builder system and integration system

I need to some modifications and coding for websitebuilder and add some modules for my website and WHMCS. 1. People will register to WHMCS. 2. Users can buy website builder premium with monthly subscription or use free websites builder with WHMCS 3. Users can see their website builder product in client dashboard they can update or downgrade their package with whmcs than they only need to click start building 4. It will automacitly create an account with whmcs and users can create their website after finish they will just click to publish and will connect to [login to view URL] subdomain or they can buy domain via whmcs and connect between website builder and publish. 5. They will be two package free and premium; Free package has got footer adverting this is created by [login to view URL] and some limitations like 100 MB hosting and 100 Mb bandwitch premium users doesn't have footer adverting and they have more space like 1 GB hosting and 1000 MB Bandwich. they can also connect with special domain like [login to view URL] via buying new domain from whmcs or they can transfer to us. 6. Ftp section will be stay and system automatically detect server ip from WHMCS. to users can create sub folders websites. You will also provide a documentation like explanations for changes of codes or in database because i might be work on it myself for future changes. And also the support for any mistakes or error in the future.