I don't know about such a tool in a ERP system. Personally I would use LSMW to load such data, alternative eCatt (transaction SECATT) that can be used to load some variable data too. But this this feature became a kind of complicated, at least it was easier to use in the old version with 46c release, so I didn't use it anymore.
BDC recording is more in direction of programming. SAP has as well Gui Scripting, which is not allowed in our system, so I have no experience and the docu looks pretty complicated.
I know an external tool called Winshuttle which could do your job, which uses as well scripting and is therefore not allowed to use in our company.
the MASS maintenance can take data by copy paste from Excel, but only page wise. But in MEMASSPO you can only change header and item data, the delivery dates are in scheduling data and this is not available for mass maintenance. Probably because SAP did not see a business case that one has to change a delivery date en mass.