Here's an article I just read about sandbox MMO's and how there is ZERO true sandbox MMO's in existence. Wurm comes close but its animations and graphics and combat system is just terrible so it has no chance at being the first large sandbox (IMO).
The first dev team to create this sandbox MMO is going to be very successful in terms of subscriber base. Xsyon is the exact idea this article touches on, it's just way too unfinished for positive word of mouth to start spreading.
BUT I will say that Xsyon even in it's unfinished state is the closest thing to true sandbox than anything on the market.
We just need a lot more tools, rarer resources (of all kinds, everything right now is far too easy to get), extremely rare resources, and then of course a good warfare and fun combat system.
I actually think a sandbox game will be much easier to maintain in the long run.
You won't have to do many content updates as the players create the content.
You will just have to give us more tools as the game evolves. I can think of so many things, it's so easy to give a game like this depth
Why not add blacksmith and mining? Mine ores, place ores into furnace, take hot metal out, hammer it, let it cool for 2 days REAL TIME. Log back in and your armor/weapon whatever is completed ( something for the future perhaps, when we discover how to mine and smith again)
There are more steps than that in creating a piece of armor, but you catch my drift.
Give the skill systems more depth and then add more skills.
I started creating my own game in Unity but realized if Xsyon can't pull off a game like this I definitely can't.
I have plenty of great ideas but am not too good at code. I think I'm just going to compile a huge suggestions list.
After all, Jordi and the other devs coded changes to the physical world via terraforming, which seems difficult enough...I'm sure they can throw together the rest of these features if they could figure that part out...
Good luck to you guys on getting this game off the ground. I'll be making a large post here with some suggestions soon.