Dreamland, Fountain of Dreams, Yoshi's Story, Midgar (Legality: No)
With Hazards Off, these stages assume a form similar to Battlefield, but with differences from Battlefield, in terms of shape, size, platform arrangement, or blastzone. I need to explain why it would not be a good thing to have these stages legal for competition.
As I just mentioned, we have the option to change every single stage into a Battlefield or Omega variant of itself. And as I said, these are cool, standardized, and absolutely should be legal. However, something very important happened with the creation of these stages. When these stages were made, it was made so the shape, size, platform layout, and blastzones were exactly the same between each stage. Because of this, we have been given a standard for what we should consider to be "Battlefield" (and "Final Destination"). For the Hazards Off versions of the stages in this topic, all of them become Battlefield "echo stages" in that they are similar in a lot of respects, but differ in some ways, even if it's just by a bit. I would argue that we should not deviate from this very deliberate design choice, but here are some more compelling points...
The main reason against allowing echo stages like these is simply because it grants too much power to a player who wants to counterpick to a triplat stage. This should already be obvious, but if we had a ruleset where Battlefield, YS, FoD, DL, and Midgar were all legal as separate stages, then a player who wants to counterpick a triplat layout is GUARANTEED to get it unless there are 5 bans written into the ruleset (6 if you wanted to cover Lylat, too).
Obviously, one could argue that the echo stages should be combined together into a single stage choice, like how Battlefield and DL were combined in Sm4sh. However, while this fixes the immediate problem stated above, it still causes the Battlefield combo pack to have way too much counterpick power during the counterpick phase. Using Battlefield as the example; for a player who likes the triplat layout, if they get to counterpick to it, then they get the pick of the lot between five slightly different Battlefield layouts, which can provide differing advantages to the player depending on character choice, etc. If we compare this to someone who wants to counterpick, for example, SV, Lylat, or WarioWare, that player only gains access to the sole layout of that one stage, with no deviations available to them. It causes stages to have a lopsided amount of power from each other during the counterpick phase overall.
Of course, you could just say to spend your ban on the BF combo pack, but the fact of the matter is, this selection is natrually more polarizing, and will naturally draw in a larger amount of bans. If there's even one inconvenient layout within the grouping, then you would forced to spend your ban on the entire lot. In fact, we've already seen this issue with BF and DL being combined into a single stage pick in Sm4sh, and that was only combining two stages together. This grouping solution ultimately ends up causing way too much of an imbalance between the stages during the CP phase.
So here's my main point. Considering all of the imbalances and problems caused by including echo stages, the best solution to approaching them is to just ban them completely (or, failing that, legalize them exclusively under the Gentleman's Agreement).
(Also, if you have some emotional attachment to YS, FoD, DL64, or Midgar, OR if you want to have more visual variety within tournament play do not forget you can just select their standardized Battlefield form and enjoy the stage aesthetics that way. There is literally no difference.)