The only other things I can imagine are particles, and that might be going too far, I don't know. Placement of lights and particles are not deal-breakers, in my opinion, they can be redone in other software/engines reasonably quickly.
Beyond that, you are talking about the carving/merging and vis-ing of the BSP/PROC format, and I might be way off about this, but I assume those are proprietary formats and can't be used without a license, else get into some legal problems with big companies. I know this is the case with Valve, but idTech is a little cloudy. This is why we need to be especially careful within Radiant to make sure all edges and vertices align, so we can smooth everything nicely, and also split up the maps into what I call "sectors" so the LOD can function and the whole thing can be portalised. Then the BSP/PROC compiling process isn't much use to us anyway, compared to the ability to LOD _everything_, which idTech could never do.
A small price to pay to be able to stick with beloved Radiant, because you just can't make 3D environments any faster, even very high-detailed ones using modern standards, into the millions of triangles.