Hi Jaime,
currently we do not have an automatic process for the processes described by you.
For the netting of AP and AR items of the same business partner we have a manual process, which is described by my colleagues in this SCN group, e.g. in http://scn.sap.com/thread/3815248
For the central payment part SAP has a separate product, which offers also this functionality. Please refer to following link. http://go.sap.com/solution/lob/finance/treasury-financial-risk-management.html
Please let me know, if you have additional questions.
Best regards
Marlene