Summary of multiple contracts for single customer

Hello Experts,

My question is similar to the ones raised in the following links

http://scn.sap.com/thread/3632454

http://scn.sap.com/thread/3564853

There is a situation where a client has multiple contracts and each is posted separately. However, the requirement is to summarize contracts per client so that only one document is posted. This is to reduce workload of finance when clearing.

So far what i understand is that summarization can be done within a contract but not across contracts by SAP standard.

However, some possible solutions were proposed in one of the links above, namely the use of the following BADI's

1. BADI_RERA_DOC_SPLIT : (You can define the criteria for "Posting Document Splitting".)
2. BADI_REEX_FI_BAPI : (Changes Document Data Before Call of FI BAPI)

Another solution involved creating a custom version of tcode rerapp

These are my questions:

1. Has anyone successfully carried out a customization where they did a summary across contracts?
2. Did they use the BADI's above? Custom version of RERAPP? If not how did they do it?
3. There is a claim that SAP does nor recommend the use of the BADI's, this means that it should not be attempted at all or proceed at your on risk?