Dynamic exposing is not possible in FME. But there are ways to make this work. Can you describe how it should work? What are your inputs? A file geodatabase and a csv with requirements? Are you checking attribute names or attribute values?

Hi,

User will read the gdb with feature layers and search for attributes that match specified regex with the use of AttributeValueSearcher

But the AttributeValueSearcher does not need the attributes to be exposed to work? Then why and try to expose them? You can simply use the result list from the AttributeValueSearcher to communicate back the search results.

I can imagine you want to ignore all fme_ attributes, and you know which those are beforehand, so these can be exposed the usual way.

I know this (dynamic workspace handling) is a hard thing to understand, but if you do not know the attributes beforehand, you can not assign them in the transformers downstream. So there is no use to try and dynamically expose attributes, because workbench does not work that way.