Well, Sketchup and BSP are so disparate in their mechanics, I don't think you'll ever get them to work interchangably.
Sketchup exports only .kmz and .skp format files, none of which are compatible with BSP. BSP isn't that hard anyway, if you can work Sketchup then you can at least have a good go at BSP. There are lots of tutorials in the stickies to help you, and a lot of us on hand to give you BSP advice.
At the very least, your Sketchup versions can be used as advanced concept sketches for designing your map, the sort of thing I personally find very helpful to the map making process.
- Dagless