Hey, sorry if this is necroposting but I haven't been on imgflip for a while.
In no particular order:
1. Beedle's been around since 2002, if I remember correctly, and never has lore. Like Tingle... (and you know what happened when they gave *him* an explanation and backstory...) Although I'm surprised he didn't have his own shop, at least.
2. The dragons weren't important to Breath of the Wild's story (ToTK is a very different matter, but then again HW:AoC came out way before that). I don't see how they would introduce them to the story, and it would be very difficult to work them in as playable, although that would be *cool*. They don't attack anything (again, two exceptions, but that was ToTK), tending to remain "aloof", I suppose. Dragons can also only be seen by "those who are pure of heart" or something.
3. I assume by the "dragon of shadows" you mean Calamity Ganon's spirit form?
4. Wolf Link would be cool, but NPCs are completely useless in AoC. Amiibos are generally unexciting. Malanya wouldn't be interesting considering there are also playable Great Fairies.
6. Whilst the Harbinger would be fun, we already have both Terrako and Calamity Ganon as playable characters. Astor... yeah, he'd be splendid, albeit creepy, to play as. I was confused as to why we didn't get him. (Although Sooga is better.) The blights would be no fun at all to play as, I think. From my memory of the boss fights, they're too unwieldy.
7. "It is never explained just why Ganon and many other characters become playable characters". Yes. Sure. But what exactly do you *mean* by Playable Characters? Of course, we (as the Player) do not exist in Hyrule. We are not canon. Ganon is a reward, no more canon than the fact that you can replay levels as unlocked characters to have silly things like Sooga defending Gerudo Town from the rest of the Yiga Clan, including himself and Kohga. It's not canon - just fun for the player. AoC's gameplay style lends itself to this.
8. I definitely agree with the flashing-lights strobing thing, though. The fact that HW is a hack-and-slash button-mashing game makes the gameplay less fun than, say, BoTW. It's a fun little game in its own right, I think.
Anyway, it's been maybe a year since I've played it, so it's possible my memory isn't up to scratch.