Chrome/Google CMS plugin

Description

This in a tentative initial inquiry to see out people who might be able to create a stable and secure CRM type plugin for Google Chrome (and if possible Safari too) that will integrate with GoogleDrive.
What I'm after is something that works a bit like Streak https://www.streak.com where all the data is held on the user's Google account.
This is for a very specific need for one industry rather than seeking to build something as complex as Streak.
It is not a sales platform - just a place for researchers to collate data.
However, I need to be able to: -Have a range of subscription packages for users to sign up to-Allow a 'master user' in each workplace to manage sub-users-For multiple projects / teams to be created within that workplace - and access controlled by the manager-For all data to be stored on the client end (in GoogleDrive/Docs) and for them to be able to download backups-To be able to produce reports within the CRM based on the data-It must be secure.
Rather than outline all the details of what I'm after at this stage, I'm looking to hear from people who have the SPECIFIC experience producing plugins of this type and successfully launching them. If you do happen to have an idea of costs based on previous projects, then do let me know.
**IGNORE THE BUDGET BELOW I JUST HAD TO PUT SOMETHING IN**
Thanks