Walk-offs are already improved to the point of viability in Balanced Brawl; that was an explicit goal I feel we accomplished already. Chaingrabs and locks that lead off walk-offs simply don't exist in Balanced Brawl; we removed all of them (with the exception of ICs chaingrab potentially having some walk-off power, but ICs are a special case and everyone knows it). "Walk off camping" doesn't work in real games with decent to good players, and most insistence that it does come from people who have little experience on walk off stages.
In general the idea of "fighting the stage" is just nonsense as well. Decent to good players don't have trouble surviving on any stage. Really, set yourself to Ganondorf (the least mobile character) in training mode, go to Rumble Falls, and see if you can survive indefinitely. If the answer is no, you really, really suck at Brawl, so bad you should go, play, and get better before posting on smashboards again. The point there is that the stage itself is a non-threat. What is dangerous is when the other player utilizes the stage's geography and features to force you into peril. Some types of geography and features can be overly polarizing or promote degenerate gameplay, and Balanced Brawl seeks to remove those. however, geography and features that create peril in general are no evil; having to respond to a Meta Knight on your left and a wall of lava on your right and finding the solution that ends with you still having your stock and hopefully the Meta Knight not having his is an essential part of Brawl. Non-traditional gameplay isn't a particular problem either; winning because you were able to control horizontal space well on Final Destination is no more or less valid a victory than winning because you were able to pin your opponent on the conveyor belts in the electric form of Pokemon Stadium 2 (there is no reason for Pokemon Stadium 2 to not be legal everywhere in standard Brawl already; people are just dumb about it). It's all a part of the game, all the changes in Balanced Brawl are definitely made to consider the depth of possible situations that could arise, and to be very blunt about it, the game is just plain better when as many very different stages as possible are preserved and used in a serious competitive sense seeing as every unique feature offered by a stage is just a raw addition to the depth of the game.
Now as per the three dramatic stages Lokee brings up...
For one, Mario Bros is definitely the structurally worst of them, and I have no idea where one would even start in trying to make it fair. The hazards are so powerful nothing else even matters, but I think the stage would actually get worse if the hazards were toned down or gone since then things like the massive loop or the way the stage is a huge techfest would start to matter and would be even more broken than the hazards (the hazards just basically make every character the same since "throw a turtle or crab" is a better attack than literally every character specific move in the game). This stage would be one of the very last I'd consider trying to save; in addition to being probably the most fundamentally flawed stage in Brawl, it also has to consider that the "soul" of the stage requires almost all of its features be left in-tact (or else it would not be an accurate re-creation of Mario Bros!). Eventually, maybe severely weakening (but not removing) the hazards and letting the platforms be passed through could work, but there are issues with that still.
75m isn't such a bad stage; the only real challenge is the fact that changing the structure of it at all would make it, well, not 75m. Ladders are awesome and do nothing but add to the stage's virtue, and the hazards aren't that big of a deal (the springs could probably afford to do less knockback, but it's a small issue not a large one). The main problem the stage has is that the multitude of really small platforms makes certain types of camping way too good and low aerial mobility characters way too bad. Camping the lower-left is what I've found is the best tactic in general; you have to jump in on that to approach it, and your safe options to do so as most characters are really limited. Ness in particular is really silly from this position as Pk Thunder can actually still pressure from here, and the left blastzone isn't really that far so he can actually fthrow to kill stupidly low in that direction. There are also some strategies for camping the lower-right that can be pretty effective, though I don't think they're as good as the lower-left ones. Either way, characters like Bowser and Ganondorf are just hopeless; they can't approach any of these good defensive positions without great tribulation, and anything they might try to do is telegraphed massively because of how long it takes them to do anything. The stage also is pretty good for certain types of run-away which can be silly. Fixing it is mostly hard because the lay-out of the platforms is an essential part of the stage being 75m. I'm not going to destroy the authenticity of these retro stages like that...
It's not the topic, but Hanenbow has similar issues though a little different. Basically, the small platform camping is just really good but not quite broken on Hanenbow, but the run-away, instead of being really good but not quite broken like it is on 75m, is actually broken on Hanenbow. I do have an idea to improve Hanenbow; I'll have to figure out a bigger strategy to deal with that and the stage select screen.
Flat Zone 2 is actually just a skip and a hop away from being fair. With the walk-off issues resolved, the main issue is that the lion tamers are just way too powerful. If we could edit the hazard hitboxes to tone them down, Flat Zone 2 is instantly cp worthy... though somewhat of a tone down to the oil panic guys might be a good idea too. The main concern is actually that Flat Zone 2 is just a really, really good Snake stage; the ceiling is lower than average (though not as low as some silly people seem to think; it's much higher than Flat Zone's ceiling from melee), and he can utilize the hazards as a part of his spatial control game very efficiently. Still though, with stage hazard editing, it should be workable.
With BrawlWall under such active development though, I think we should sit back and let Dantarion work before getting too excited. I definitely intend to make use of these new and exciting tools, but as things stand we still have some waiting before it will be clear what exactly we can do.
I still need to find Nana's subaction offsets for dsmash and pummel, and then I can get that .pac done. I normally do .pacs in one shot, but I spent over an hour digging through PSA looking for that dsmash just not finding it for some stupid reason or another and had to take what I will euphemistically call a sanity break... and haven't had a chance to look at it since. If anyone's curious, here are the offsets I've found... as proof I really have done something.
Nana's dair subaction: 2d234
Nana's fsmash subaction: 2c1e4
Nana's usmash subaction: 2c3e4
The throws are already known, just in case anyone was curious about that.