Connecting Lead - Quotation - BOM - Site Survey (custom doctype)

Hello there! This is my first participation and question to the community. In one sentence, I am using ERPNext deployed in AWS, willing to customize it for Solar EPC business, which requires some customization (like almost any other business) to suit and ease the usability and convenience of the ERP operations by the staffs.
The requirement is as follows :

  1. A lead is created.
  2. It is linked with ONE site survey which can select items and its quantity (in item group of BOS materials) for example, variety of cables, electrical items, etc.
  3. These items are then calculated with the pricing.
  4. While quotation is created, the master item is selected, additionally the total cost of the site survey items are added in the quotation.

Thank you for your time in answering my query.