Mark,
I fail to see how this helps you.....just because you rename it does not change the block.... The name of the block is the same as the block definition. A block reference cannot have a different name than the block definition...
Did you think about the solution I mentioned? I mean the "save multiple Wblocks of the same block with the desired layers for the different scales....that, to me, is by far your best scenario.
IOW, take your base block; change the layers to match what they'd be for a 48 scale insert; SaveAs BA-SYMB-48; now change the layers to -96 and SaveAs BA-SYMB-96 and so on. Then have your code insert the proper block based on the scale.....then change the layer of the insert to the matching scale layer.....too easy, no having to rename blocks and layers, or check if the layers exist....the only thing I'd check for is if the block is already in the drawing, if it is just insert it, if not then grab the one on disk. This should also fix your exploding problem, too.