The problem with error message converted to warning for credit limit would occur in case the confirmed quantity is increased for items relevant for credit exposure update.
This could happen when:
- you had partial confirmation for some items (delivery block with confirmation reset or insufficient stocks)
- you increased the quantity in the sales order manually (item quantity, new item)
- you changed an item category (tann->tan)
- you reduce the credit limit and run recreation of credit data etc.
Analysis means to determine which reason causes the subsequent credit limit blocks, so that you can target it specifically.
From business perspective - are the credit limits optimally adjusted? What about seasonal factors and the business impact on credit limits?
If the customers exceed too often the credit limits, why don't you re-classify them, so that they pay either at the time of delivery or even in advance?
In addition - I can see some valid business reasons to let an order blocked for credit limit pass through.
As to your question - I would not go for development at all, unless I have exhausted all other available options to solve the issue, but if you really insist to do that, Michael Kozlowski already pointed out the most appropriate exits.
If the credit manager releases the orders without performing investigation, then it makes very little sense to have a credit control manager, because there is not much control on what gets through and there is no management taking place. 
SAP can solve technical problems, but in this case getting some knowleadgeable persons in credit risk analysis as advisors or organizing workshops to revise the current company procedures for credit account processing would be way more appropriate.