What I liked about UO the most was the option for Freeshards. The official UO servers weren't much different from the hack, slay and loot WoW gameplay yet the deepest and most positive experience I had is connected to Freeshards where roleplay and immersion were king and you had to use your own fantasy to create a character and a world. It's a unique experience I haven't seen before or after and to build on your own world, create your own houses, cities, dungeons and society and interact with people that you really got to know in the process of playing together was awesome. It wasn't so much an MMO as an interactive roleplay game where every freeshard had a different story and setting.
I can't express how much I would love Sui Generis to fill those shoes yet I can accept if multiplayer ain't possible.
It's not that it would be that simple anyway. Even though you only would have to provide and sell a matrix to the players (maybe with some add ons here and there with new items, features and so on) and the players would do the rest and create their own worlds you would still need a lot of features that Sui Generis as a single player game hasn't planned.
Starting with a simple yet detailed world creation tool, same for player created quests, a tool for mods to overseer the gameplay and interact withit, a dedicated pvp system, an architecture feature to be able to construct your own house when you provide the building material, a lot of crafting from forging to tailoring to carpentering and even baking or cattle breeding and farm work. To make a long story short: It would be an entirely different game & concept.
I hope Sui Generis will become a big success. Whenever I see some new information or a new video it just shouts Innovation! and Immersion! as never seen before. The whole package keeps surprising me over and over again and leaves that pleasureable feeling of "what if?" as the vision of the devs manages to inspire you to dream. Maybe on a future day after Sui Generis has been released you may aspire such a project.. with or without a cooperation with Richard Garriott. I really hope so.