how to create a drag and drop website builder

Introduction

My company needs to build a Website Builder platform and I was tasked to gather all the needed Information and technologies needed.
It will be used to create a simple admin dashboards for our customers to be able to login and view reports done by our company, it will be personalized according to each customer but it will mostly have the same layout and components
e.g:

Same:

  • headers
  • same amount of pages
  • mostly same amount of objects

but will differ in:

  • colors
  • text
  • some additional tables that will be added according to each customer.

so overall the template itself won’t change that much but the design will.

Basic Information

  • After completing the project it is expected to be used by a “non-developer” employee so it needs to be user friendly and mostly use the GUI to interact with the project to create the website with as little coding as possible.
  • It is highly preferred if it is done as a browser based project not an application since it needs to be accessible in both Mac and Windows systems as well as the ability to use it in mobile/iPad systems.
  • It must be an in house project so can’t just use something like WIX or squarespace
  • I know its a mammoth task but I am not doing it alone, we have a team of developers and I am just gathering information and ideas.

what’s expected form the answers

  • Any good additional ideas/Modifications to improve this project
  • Overall step by step of how to achieve this project if possible (like you should do this then this but not like a detailed tutorial of course)
  • Technologies Recommendations to be used (languages, libraries, etc..)

Note: To eliminate confusion Whenever I mention “Project” I mean the “Website builder” itself

Thanks in advance