The two existing attacks against bitlocker are quite a stretch. Gaining access to the victims computer TWO TIMES is a very unlikely event. What will happen in most cases? The Laptop/Workstation gets stolen alltogether or just the harddrive. BitLocker will keep your data "safe" (of course there is NEVER a 100% security).
Only CEO data is important? Really? I think I can do a whole lot of damage with some random employees files.
"Since you can hardly expect the user to store his notebook and flash drive separately [...]"
If you are unable to teach the employees basic security bahaviour, most of your precautions will fail.
Don't get me wrong here, but security isn't done the simple way :)