I know there was still some threads about the sandboxing feature.
Here a little list of threads in which it was discussed:
My intension of the thread is, to discuss about your favourite sandbox feeling.
That can be the kind of sandbox you prefer or the possibilities of sandboxgaming.
For me there are some examples of sandboxes and my result of likes and don't likes of them:
On first i want to mention Salem the Game, because its a balanced MMO-Sandbox that i liked most:
- it is a openworld sandbox with deep PVP aspect, not farmville with combat, more Mortal Combat with Corn.
- you can claim/build wherever you want (with some few restrictions on Mountain biomes and public areas)
- you can lose your claim and progress in reason of several actions by other players
- you can lose all your stuff or even your characters (permadeath)
- but you are able to defend your stuff, if you learned get to used to the mechanics
- for bad things that happens is a crime system implemented (just for completion the aspect of destroying)
- you can change ground (digging or filling up)
- you can change biomes
- for building your personal or town claim you have a set of buildings that you can arrange
- That part is prefab building, but thats okay, because the focus of sandboxing is on designing the claim and saving your stuff.
- Most buildings and structures have a functionality for crafting, storing or defending.
- There are some decoration items for the girls between us who want to build up our "dollhouse"

My conclusion: Even the gamegraphic is surely nothing most would play in 2018, it was till now one of the most balanced and themed sandboxing i played. I know i would not fascinate much of you into the game itself, but it is definetivly worth to get some ideas of mechanics from it.
I was also reading about Minecraft, that was mentioned on some other threads.
Minecraft is (beside just playing with "ugly" blocks) one of the coolest sandboxing game ever, because of its possibility to create whatever you want. It's strength based on it's modularity.
But for a special themed game it would not be the right setting.
I mean a themed game itself should not lose its special character and atmosphere, just because player are too free in creating things. Well, in Minecraft you are still limited by the set of possibilities that the Serverowner gives in your hands.
Lets just make a little discourse into Pseudo Sandboxing, there are many examples, that is going from just own homeplots/hideouts/housing everyone in a single instance, till the Housing/Sandboxing Areas for a group of players.
I don't want to see this kind in Fractured, because it seperates people from each other. If you have such a Pseudo Sandbox, you will spend most time alone in your little instanced housing area and "never" get in any interaction with other players.
I want to mention platforms like Second Life too, even it is not a game.
I think we can agree all together, that Second Life kind platforms are the greatest Sandboxes ever, because of the just user created content. I don't want to discuss Second Life or similar Platforms itself, because that does not matter for a themed game.
But i want to point on the repeating questions by player in sandbox games: "Are we allowed to upload own created things."
To be honest, yes i would like it if it would be possible with limits. I think it would give a game a next step on interaction.
But i think for such user uploaded content it needs a special team of moderation, that decide if the upload will be legal.
Beside the look of things, from just textures to own structures (like Statues or Totems or whatever) i also think on player created quests.
I missed in most themed games the possibility of player created tasks, that you can store ingame and make it accessible to other player. I used in much other Non-Sandbox games third-party scripts for it (like lua scripts in WoW), but it has always the problem, that the player created quest is not available, if you are not online at same time.
My conclusion for it: To have a limited system to create playermade content would be great and surely an unique point for a game that want to be other than others.
I know that the last point i mentioned was implemented in UO, i sadly never played it.
But i ask myself always, why no (well known) game after UO took up these cool features. Maybe it was, because the gamer community turned lazy and just wanted light consuming of prefabed themeparks. After they played them now for many years, the gamer start to remember or the younger ones are just supersaturated by always same mash. Who knows.
What do YOU wish for a grandios Sandbox feeling that don't break the game theme?