Alright, so now that I've finished it, some more complete thoughts. Overall, I quite like the quest.
The things done to the OW are really cool, especially level 3 being part of the OW, as I mentioned above. I think my biggest gripe with it is how you're somewhat railroaded through it. There's plenty of secrets to find, but there's definitely a sense of wandering through a fenced off playground and discovering areas as the game deems it appropriate. With that said, it's pretty competently put together. It does walk a fine line between being the Z1 OW and being its own thing, and some areas nail this feeling, while some screens are basically unrecognizable. I think whether or not that's good or bad is a matter of perspective.
The dungeons are generally pretty good. There is a somewhat stark and noticeable difference between Team's and Rain's dungeons, with the former being more condense and filled with room sized puzzles, and the latter being more open with a macro-sized dungeon navigation puzzle and more open screen design. I think, for the most part, that works to the quest's advantage. I love Team dungeons, but they can at times be very densely packed with puzzles (less so here than in Eiyuu), so Rain's provide a nice breather, making you think in different ways and preventing the feeling of jumping from one brainteaser to the next. I liked almost all the dungeons (especially the way you go into level 3 multiple times, as I mentioned above), though the final dungeon did have a bit more swinging back and forth from one side to the other than I'd prefer. The minidungeons that are new to definitive edition are all great.
The quest's use of items was solid. Really cool puzzles from the items, a few creative uses of them, and consistent triggers.
The story... was there. It wasn't bad, but nothing standout either. I did like a few things about it (the way Ganon was used, for example), and the unexplained elements (the eyes) were intriguing, but I definitely get the sense that there's a lot more ideas in the dev team's mind than actually made it into the quest. Definitely curious to see what's done with it in this remaster they're cooking up.
Overall, it's really good. My biggest suggestions for the remaster (and I've already mentioned some) would be as follows. I'd allow for some degree of nonlinearity when possible. For example, L2 should be clearable before L1. L8 requires L7's dungeon item to reach its own dungeon item, but otherwise can be cleared without, so it'd be neat if it were possible to do it earlier. Really, just small tweaks that still push you in a certain order, but allow for some coloring outside the lines. It'd also be nice to have some kind of system to track the Master Ore. There was only piece I forgot to go back to and probably would've found it with a bit of exploring, but if you're missing one single piece and the only option is to comb over the entire world repeatedly, it could get a bit annoying. Ideally, some kind of system, only accessible post-L8, that hints at missing locations without outright spelling it out would be nice.
Again, really looking forward to seeing what you all come up with for the remaster.