came across this external BD Rom: [Register or Login to view links]
It got me thinking whether it is possible to use it on a PS3 and if it would allow blu rays from a different region.
I didn't try to connect an external BD Rom to my PS3 but I bet it won't work at all. Technically, there are two different command sets to access flash/hard Drives and optical drives so an external BD Rom can't be accessed as a typical storage device. I doubt SCE put USB optical device driver in the PS3 firmware.
Besides PS3 is region-locked device despite of its ability to play PS3 games from other regions since PS1/PS2/DVD/BD region restrictions are still here and it would be it would be unbelievable to imagine a PS3 allowing to change BD drive region five times like PC software does.