It is certainly true to say there are developers out there with games "similar" to Ultima Online. Take Albion online for example, but there are things which are really not good ideas for a sandbox game. I long for a simple sandbox game (simple but with lots of sandbox elements, lots of CONTENT) and nice visuals like pillars of eternity or something similar.
Just some specific things I think would be better for sandbox games.
Less is more with sandbox games.
What I mean by this is lots of useless systems and game mechanics. A lot of new developers are trying to create intuitive combat systems etc... People still love runescape to this day and its not exactly complex, sandbox games are not specifically about the combat. I actually loved the simplicity of the systems, but large amount of content, for the various trade and combat skills in UO. If lots of development was just put into creating lots and lots of content to create LOTS of different trade skills and combat skills (like UO has parrying, anatomy, mace wielding, fencing, hand to hand, etc etc for combat and pottery, cartography, taming, alchemy etc etc) it would be better than putting development into fancy combat systems. Another example of a good sandbox game although not mmo... Terraria lots of content, simple systems.
Very simple UI.
No need for all the bullshit. I don't want to play a UI, I want to play my character.
Please no mini map and have a large scale world.
Especially with FFA pvp and full loot, if the world is very large scale and people don't actually know what is ahead, it makes for a much more personal adventure and less likely to always be hunted down and killed by people who outgun you or who are just roaming for kills in a group.
In Albion Online, one aspect of concern is the fact that groups are going to run around killing everyone, if you are not in a group/guild, you are screwed. UO was not like this generally and I think the reason is that the scale of the world (and where you would spawn and the fact there was not always just literally like 3 specific ways to get out of a city) and the fact there was no mini map, meant that there was a massive chance you would not actually be found and could adventure away solo if you wished.
Started playing mmorpg's in 1996 and have been hooked ever since. It began with The Kingdom of Drakkar, Ultima Online, Everquest, DAoC, WoW...