1. Create an onMessage microsite. When creating a new site, there is a way to add custom CSS code and Javascript on a page with an Embed Widget. However, there are some Javascript restrictions where it's locked down. 
  2. Blackbaud has a billable design service which includes five conference calls to field questions about whether something is possible, however it does not include writing any scripts or making any changes to the existing software. 
  3. A button could be added to the footer of the main site that could point to an external custom site.