First off, don't send me to /r/minecraftsuggestions, since I made that post there, and it got a really low exposure. Lately /r/minecraft had a lot of suggestions, so why not chime in.

This is somehow often suggested, but what about make this big, in order to get more attention of devs?

Because it's too dangerous to go alone, i'll take this would be a great feature that could change Minecraft experience drastically, i'm going to make some sort of post "collaboration".

Hyta's suggestion

There was a suggestion 3 years ago made by /u/Hyta, it's 5th in top of all suggestion posts
It has infographics (mobile users warning: rather large pic) that is pretty much close to what I and many users suggested. Though the idea of server is bad, you can read why below.

Wedhro's suggestion

To continue the idea, i'll adapt text from post that has been made by /u/Wedhro today

Imagine that we could build our own semi-random structures and put them in the world save together with a few spawning rules so that the world generator could automatically create such builds like it does for villages, temples and so on.

Everything Mojang said or hinted about structure blocks is only meant for map makers, and this is a huge waste of potential: map makers already found a way to generate builds on the fly, in a very inefficient and convoluted way, so if structure blocks were limited to them it would be a nice help, but it would not open a new world of possibilities.

People creating all kind of procedural structures and sharing them on websites, so that one can tailor its own SSP experience. People could create a large variety of dungeons, villages with actually different building styles, custom trees, literally anything one could think of, and then anyone could pick the ones they like and put them in their own worlds. Servers could create their own structures and not share them to provide an unique experience.

The current system only needs a file for giving rules for any structure: in which biome(s) it's spawned, how many "rooms" it should have and so on.

My suggestion

Being a creator:

1. Make a structure (using any blocks in MC and a structure void that will fill up with blocks in MC world, so it won't look unattached to world)
2. Give it settings (see 'Settings' below)
3. Save it
4. Upload (or make a few, or more, put in zip)

Being a player:

1. Download
2. Put in Structure packs (as if you would change your resource packs, but no hierarchy needed)
3. Play!

Settings:

• Position (underground, in liquid, on the surface or in the sky?) by /u/MasterDisaster64
• What biomes structure should generate in?
• What mobs will spawn around the structure
• Loot inside the containers (use loot tables?)
• Effects (buff's/debuff's, some visual-only effects?)
• Ambiance (oh oh! Mojang, add an ambiance feature!)
• Collision with other structure rules
• Linked to other structures (rooms)
• Amount of structures per world (certain amount or infinite) by /u/MasterDisaster64
• 'ruined noise' effect (like certain blocks can be absent)

And I think we need a fancy settings editor for structure. Won't matter if implementing that would take a whole version (1.11 – Infinite exploration update), or few versions…^{1.8 mod api half-life 3}

Why the idea of server is bad

Because Mojang would have to make a lot of changes, including hiring people who would moderate the builds (imagine, thousand of noob-pillars, gold penises, 'wooden boxes', swastika's and many-many other bad things). They should leave it to us, as with Resource Packs. I think Curse will make another category for Structure Packs. Yes, they must be separated from Resource Packs.

Still not convinced?

This idea will make Minecraft literally endless to explore. I mean Endless with a meaning of huge interest in it. Endless experience. It will take a lot of time to become bored of exploration of the unknown. I already can imagine Structure Packs threads with screenshots that shows only small portion of structures, or no structures at all, in order to make players not know what they will see in-game.

It's the feature that will never get old.
New block? Ok, we'll use it in my next structure. New mob? Neat. Will fit my structure nicely.
And so on…

This game will gain soooo much interest again. So much players left because they're no more interested in exploration, because of it's repetitiveness. Players will be always inspired to explore the world. With those custom structures you will play Minecraft almost the way as you did the first time!

…What about more customization?

I don't know what you might say about next idea, but I feel that I should suggest what they should add next: the ability to make custom mobs, blocks, items, entities in same fashion as structures (with fancy and easy to understand interface) and we're done.
Mojang will move to squashing bugs, improving graphics, adding mechanics, if you think, there is still many thing they could add, even after this. But if they'll stop adding anything, that won't be a problem. Only the imagination will be a limit. And that's it. Game will become infinite. You will be able to make your adventure… Yes, people making awesome adventures already, and now imagine what we'll see with this features? And all of this on servers… Wait, what adventures? We'll be able to create a whole new games! The only distinction will be a blockiness.
Anyone will be able to become game-maker. And i'm not even looking at all these attempts of make 'game making inside a game' that we saw before (for example, Spore: Galactic Adventures)
I know that it might sound like the features that we'll never see, but who knows… Maybe after the moment when Minecraft main version will be the one that written on C++ (Currently, MC:PE/MC:W10E). Could become something like Gamecraft (just an example, it can be Minecraft 2.0, the real one)

Possible downsides (and how to avoid them):

• New/young players could be confused (create a tutorial, make interface easy to understand)
• Editor will be rather hard to implement (hire good programmers…?)
• New structures could conflict with each other (can happen only if the setup is bad)
• Extra lag in world generation (i'm pretty sure won't happen if it will be added on C++ version, otherwise we can't avoid it anyhow. Lag won't be that extreme though)

Maybe I'll make some infographics later too.

tl;dr: mejeng pls add I-made houses