Mandatory Fields for organizations' creation- I need your feedback and experience

Hello, 

I would like to add a mandatory field to fill while creating an organization on Zendesk. This mandatory field would be the ID of the organization on our tool. I would be very useful to have it then for many KPIs and analysis. 

Have you had the same need? How could you resolve it please? Because Zendesk does not allow this :( 

Thank you :)