Petition Website Build

Example Website:
https://www.change.org/

Platform:
I'm thinking a Wordpress site, but I'm open to suggestions. The key is to enable cosmetic changes via a CMS.

Key Features:
Includes but not limited to:
- Ability to store and extract data of users who create an account (i.e. petition creators) and sign a petition.
- Collect and store user consent at the point of a) creating an account b) signing a petition (consent for wording to be shared later).
- Website to display most viewed/clicked petitions on homepage/existing petitions page for high traffic visibility.
- Enable petitioners to pay for increased visibility of their petition within designated 'ad space'
- UI where users can create petitions, sign petitions, download CSV and official letterhead of petition signatures (CSV to contain list of email addresses partially asterisked for data protection purposes).
- Social sharing options as well as a copy and paste URL to gain signatures
- Gamified progress bars to represent meeting signature targets (100, 200, 500, 1,000, 10,000+)

This is the initial brief but I'm keen to develop over time so this is likely to be an ongoing project.