Looks as though someone else has already submitted the idea @ SAP Idea Place - Ability to turn off delegated measures in webi reports based on BEx queries (BICS connetions)
To Ingo's point which I have seen raised on multiple posts, we completely appreciate that Web Intelligence is not an OLAP tool but in these instances the Analysis products (which we utilise) do not suffice. Our users leverage Web Intelligence frequently as a powerful self service tool against BW data to (among other things) create variables (custom dimensions & measures) at the report level without engaging IT. This is not possible in Analysis and proves difficult in Web Intelligence when having to combat with these scenarios.