I think you might be in an alternate reality if you think series land rovers were manufactured by BL. Even if Rover and BL were merged, Rovers were built by Rover. I've owned a few, currently have 2 of them so not sure who you are trying to convince.
yes, but the Rover plant was always the Rover plant and Rover engineering was always Rover engineering. Shared resources doesn't make a Montego a Rover any more than silicon valley makes Yahoo a part of Apple. It just helped ruin Rover for good.
Rover has had its own failures though. Poor electrical build quality in a lot of older stuff (much like many British cars of the past, sadly. Never look behind the dash of a mini). The Rover 214Si for example had a _very_ common failure resulting in a warped head if you were only slightly unlucky because they decided to get cheap with the head gasket.
Shortcuts and money worries may lead to creative solutions, but they just as readily lead to heartbreak and failure.