Thanks a lot for your clear answer,
Use the classification view is the best option I think because there are standar tcodes like mmcl that can provide inventory list from characteristics "groupers" like I need, but unfortunately this is at material level and my business scenario has the same material code in different plants with different grouper, so it would not work for me. I think I will go deeper with my Abap team for the option you mentioned about " An append structure with your own Z-fields to MARC." or finally sacrifice some fields that are empty with low potential to be used in material master and build a zmb52 that track inventory from them.
Thanks a lot
Jorge G