Hierarchical Instanced Static Mesh - tedious to build and LOD problems

As part of an optimisation pass we are starting to make use of HISMs for background actors and such. The only way we can currently do this is by copying and pasting the position, rotation and scale parameters for each mesh in the HISM which is RSI-inducingly painful when dealing with hundreds of actors.

What we really need is a way to select actors in the level and conveniently convert them into a HISM without having to build the HISM from scratch.

LOD distances also seem to have little/no control so meshes appear to render at the lowest LOD unless you get very very close.