@jorge, one of the ways around this I have found is take an additional query of the data and place it in your data cube. The only piece of information you will want here is the value you are trying to capture (WHM, WPP, etc.) From here select the distinct list of all the values. Join it with your data input you are querying from, you will want a right or left join based on what table is primary.
From here you can take the variable from your query with all distinct variables and make it your row or slicer. If you want to have it show up in the rows, go to the measure, and for missing data input rule select “Full nulls” I have selected 0 for illustration purposes.
In my example, 9/20 does not contain any info for member no. 1 but it still shows from the sourcing of nulls and the join.
Raw data snapshot
Hope this helps, like @ken said, its a bit of a pain.