We could make List of blocks in Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey so that we can make everyone find all the blocks and thus be able to complete the game 100% the reason is that I can not take the screenshots in a good way.
First, the game you listed is the wrong game to make such a list. The original Mario & Luigi: Bowser's Inside Story game is the game you want to focus on rather than its remake unless the remake has changed areas and even so, it would still heavily base its content off the original game.
Second, we don't really specify where blocks appear in any game, not just Bowser's Inside Story: it extends to Partners in Time and Superstar Saga. We might talk about their locations in the area specific articles but I don't think blocks warrant a list, as they're very broad and highly encompassing, making it difficult to keep track of unlike bean locations and hidden blocks. I don't even know if it even goes towards 100% completion.
Unless of course you are referring to hidden blocks rather than generic blocks in Bowser's Inside Story. If so, you're free to make such an article, but keep in mind that other editors aren't obliged to take on requests.
I think what you say is good and I mean the blocks in general that would be the normal and invisible ones and I also think it's good what you say with the new articles you mention and don't forget that Mario & Luigi: Bowser's Inside Story + Bowser Jr .'s Journey being a remake can have blocks in different places.
It does help with 100% completion, but that's not the wiki's ultimate goal. I don't think creating a list of every single block appearance in a game would suffice because otherwise, we'd probably have to make articles for every single instance of blocks in every single game for consistency. Hidden blocks I can understand that we do need their locations for in Bowser's Inside Story but not generic blocks.
Making a page for the blocks overall is excessive and unnecessary. We simply do not need to make a list like that. They can be listed in the articles where they actually appear, but an overarching list like that would be absolutely massive and a pain to create. Hidden Blocks are a circumstantial list, it depends on how the games utilize them.