Hi Emanuel,
My team and I are actually working on this and do already have an answer to your question for the current release 1506 (your new ERP with sFIN). And this answer indeed is the approach using SAP Data Services and the so called Rapid Data Migration solution. It comes as packaged solution and we're even in the process of updating it for the new S/4 release 1511 with sLOG.
Regarding the information that is available now, please check out these resources and get in touch with me:
Demo Recording:
http://www.youtube.com/watch?v=jHbBxtLR98c
Where to download the content (landing page):
http://service.sap.com/rds-dm2erpcrm
Generic Blog about Rapid Data Migration:
Hope this helps.
Best regards,
FRANK.