Now, I don't know what BSP features are planned in patch 5, but the following features are an absolute must. I worked on a number of platform action titles for Playstation and PC, and we used the following features a lot.
- Access any texture, animating and/or UV scrolling it.
- Get surface/texture properties. This could be as simple as getting the texture name or ID. Used to identify the surface. (Ice = slippery, water = spawn rings in water particles etc.)
- Transparent texture support (Is this in now? Haven't been able to make it work. If it is in, and anyone know how, please tell me

- Detail objects. These are not compiled as part of the BSP, but added to the appropriate BSP leaf for drawing more complex geometry than most BSP compilers allow (Especially solid node compilers). A simple Axis aligned BBox (standard DBPro collision) for these will suffice. They are culled with the BSP leafs, so they don't need to be processed all the time. Maybe being able to insert loaded objects into the BSP and have them auto placed/processed at the proper leafs?
Hope it makes any sense
Best regards
Ozak