What is your domain model and how is it configured? If I understand correctly you are mapping some association for eager fetching, since this is "needed". On the other hand you want lazy fetching for indexing. How do you envision this should work? You want to change the association fetching strategy just for indexing? Are you talking about the mass indexer here, btw?

Out of interest, why do you need to load these associations eagerly in your application? Lazy loading works often quite well. I am just trying to understand your use case better.

Last but not least, we have been talking about utilizing fetch plans for association indexing. In this case you would define a fetch plan for indexing purposes and somehow configure this fetch plan with Search. Is this something which would work for you?