Unfortunately, at the moment Lightroom really is frustratingly crippled as an asset manager. The only way to handle the "disconnected" situation is, basically, to maintain one database per "chunk" (might be a shoot, a week, a month or whatever) and to use something more suitable to manage your full archive. Ironically, especially given some snide comments from certain authors, effectively LR is very, very similar to CaptureOne in terms of actual, realistic functionality at present. The main difference being that CaptureOne knows it's limitations and is built around a session metaphor.
iView is a good option for heavyweight cataloging, but it has some limitations especially when to comes to managing different derivatives of a master. There are workarounds, but they're fragile and mind-numbing.
Hopefully Lightroom will be updated to manage this better in the (near) future, but if not, then I do wonder what real advantages it really offers over Bridge CS3. It seems to be designed very much for studio-based photographers at present.