User Permissions for Issue Doctype based on Dept & Territory

Dear All,
Greetings from KisanMitra Helpline.
We are trying to build a HelpDesk Application for a [Farmer Distress Helpline]using Issue Doctype as primary, and Leads, Contacts, Employees & other doctypes to support.
Lead & Contacts would be taking care of customer(in our case farmer) information when a call is received.
Issues are logged in Issue Doctype for various categories of issues & from various territories.
They are forwarded to Government Officials who belong to various departments based on category of issue. We are currently trying to model Officials as Employees within the system. There are a few customization we are doing as part of this, and would be contributed back to the core code base by MNtech Folks.
We don’t have a clarity on how to restrict access of Employees/Users on Issue Doctype for a particular Dept & terrirtory.
For e.g. A farmer reports an issue of Crop Loss from Vikarabad Mandal, Vikarabad Distrcit, Telangana State, India.
This issue comes in the category of Crop Loss, and belongs to Agriculture Department along with Revenue Department.
So Officials from Vikarabad Mandal & belonging to Agriculture & Revenue should be able to view the issue when they login and act on it.
Do let us know if someone has come across such a scenario in other doctypes.
Currently Gaurav , @unmesh, @revant_one & others from MNtech are helping us, but would also like to hear from wider community if you have any suggestions.