To enhance a component, which is not open for AET is effort consuming.
Yes, the field must find a place to live, in a table, so that it can be saved.
Please check in thread
Need to add custom field on GS_CM component under the DocList view?
which contain some article link regarding how to enhance the genil/bol with complete Z tables, regarding how to enable the save into the Z table, for example.
Hope this could do help to you.