Thanks Laszlo - this is a solid workaround, which does not require any adjustments to the material settings (which is a big plus). However it is still prone to the same problem as the solution from Nathan - what happens with materials once used as loadbearing and once as non-loadberaing (for aesthetic purposes)? I cannot see any way around it though. Even if with AC26 the components of a composite can be individually classified (which is great), the classification is done on material basis. Conclusion - the need for an adjustment of material list with loadbearing / non-loadbearing versions of the same material remains.
An update of partial structure display menu with a "non-load bearing elements only" option, which could also be used for IFC translation would be a tremendous help for working with federated models (and is particularly important in the use-case of material re-use / lifecycle management, where the model data has to be merged and duplications of geometries between federated models avoided).