Multiple membership of organization

CIVICRM does not allow to add/renew membership (online) of different membership type from same organization.

We have a requirement for one of the client that they have multiple membership. Like they have National Level membership, State Level Membership and county level memberships (3 membership type). One visitor can signup any type of membership more than one. Like one can take up National and state level membership.

CIVICRM does not allow to signup more than one membership. If someone is already a National Member and try to take State Level membership CIVICRM will update the same (national membership) start and end dates as per duration of new membership and will assign new membership replacing old (National)

This works fine when all membership associated with different organization.

We investigated and found that there is a flag that needs to set.

We feel this is generic requirement.