Hi,
Standard data source are always need to load standard info object only not for custom one.
Future changes are comes along with ecc side not only bw side. When we need changes then we need to change(at ECC and BW side) manual and move to prod.
Ex: like in GL account, when new account create in ecc side, if need that in hier str, we need to add ecc side and as well as at bw side also. future changes it won't be the same for all companies, its varies as their business. that's y sap may given enahancement or adding feasible.
Thanks