Is It Possible to Setup A Different Credit Limit For Each Customer/Site Level?

Can One Setup A Different Credit Limit For Each Customer/Site Level And Assign The Same
Usage Rule For All Customers?

See specific details questions for this scenario below:

a. Do they need to assign the same usage rule to each customer's credit profile? This would
take a lot of work.

OR

b. If no usage rule is assigned for the customer credit profile, will the operating unit
default will be used, while the credit limit of the customer/site level is used?

OR

c. I think the other way is to set assign usage rule to the profile class and do
Tools > Cascade credit usages, but let's say for now, that we don't have a credit
profile defined for the profile class. This would essentially be the same as a. only
taking away the manual work.

As per design:

Credit Limits can be set at the following 5 levels:

1) Item category
2) Bill to Site
3) Customer account
4) Party
5) Operating Unit

The above sequence is also followed while deriving the credit check details like credit
limit and order limit. Metalink note 365866.1 explains the same in a detailed way.

Now, coming to credit usage rule.Credit usage rule is needed only when multi-currency
exposure calculation or global exposure calculation(calculation of exposure across
operating units) is needed.

The credit check process behaves the following way:

1) It follows the hierarchy mentioned in the metalink note 365866.1.
2) At every level first it checks if any credit usage rule is attached at that level
or not.If there is any attached ,then it gets the credit limits order limits and the
multi-currency details from the credit usage rule set up else it gets the details
from that level credit profile set up.

E.g : Lets say customer level credit checking is enabled.So if any credit usage rule
is attached to customer or customer profile (attached to customer),then the credit
checking details are derived from usage rule set up.If no usage rule is attached to
customer or customer profile,then single currency(Transaction currency) credit
checking happens and details are picked from the customer standard form only