I'm not in favor of exploding normal "blocks" either, as one of their advantages is in reducing file size when there are multiple cases of the block in a drawing. In terms of file size, there's actually a disadvantage in having a single instance of a block present in a drawing, although there may be other reasons than file size for making the item a block.
However, this isn't a "block" question, it's a case of how to transform an entire drawing of a boat -- I assume a 3D model -- in a fairly radical way. The length will remain the same, but the height is slightly reduced and the width is slightly increased.
This could probably be done manually, eventually, but it would be much faster and easier to insert the original drawing into a new one (as a block) then adjust whichever of the XYZ scale factors need adjustment. I'd probably scale by "reference" to achieve the desired dimensions. Somewhat similar to your blocking blocks, except with another dimension in play.
Then I would certainly explode the block, and purge the block definition. Remember, the object here is to edit a whole drawing, not to create or maintain a block of any kind. After purging the unused block, the new drawing will be exactly the size of the original, except it will be miraculously transformed to the desired dimensions. The only point of a block in this whole discussion is as a temporary working method to achieve the final product.
If we didn't have the ability to explode a nonuniform block, then we'de be condemned to doing all of this in a much harder way, and we'd probably wind up stuck with a bloated and unworkable drawing -- namely, one that consists entirely of a single instance of an unexplodable block.
