Cannot remove relationship between Cases-Accounts

Hi all

I am trying to remove the relationship between Cases and Accounts module, or at least to make this relationship not mandatory.

My customer has a specific requirements that want to create Cases only for Contacts and one case is created for only one contact.

So basically what I want to achieve is to:

a) make mandatory (or remove) the relationship between Cases and Accounts

b) Remove the many to many relationship between Cases and Contacts (or at least hide it) and vice-verse

and than I can continue with creation of a new relationship One to Many between Contacts and Cases.

Regards
Ernest