Removing members from 6 gen Outline dimension, just having level 0 information

Hi,

maybe somebody can help me on something which should be pretty easy (I hope):

I have a dimension with 6 generations and about 380.000 members in generation 6 (level 0). On the other hand I have a list of 180.000 members, which should stay in that dimension (so about 200.000 could be deleted). But I have just the level 0 information. Any of the 180.000 that should stay should stay within the same roll-up tree as before. Obviously we also need to keep the data.

Was hoping a load rule with just that 1 column, defining as Generation 6 and remove unspecified would do the trick. But that was not the case