Imagine for a moment in an alternative universe. In it, Mythic had never made Warhammer Online and was still, for the most part, a darling developer of the classic MMO community. EA, though certainly no darling, decided it wanted to finally stop sitting on the Ultima Online legacy, and make a sequel (this time for real). As the stars aligned in this perfect world, so too did EA realize that Mythic was the team for the job. The team to make a MMO dream come true. That dream? Dark Age of Ultima.
Dark Age's legacy rests entirely on the successes of Mythic's realm versus realm system. The three major factions with their unique aesthetics, unique scenery, and unique classes made each faction feel far more distinct than any modern MMO equivalent. The class design, when specifically combined with the unique faction aesthetics, also made for a rather memorable and infinitely repayable experience. In particular, I think the skill-based approach to customizing your class really took the game several steps ahead of anything else at the time.
In contrast, Ultima Online's legacy does not really rest with any specific gameplay or design advancement, but rather with the overall feel of the game and its status as the grandfather of the genre. Most notable for me was Ultima Online's sheer openness and its scope, especially for the time, which aimed at bringing a living, breathing fantasy world to life via the magic of the early internet. I always felt connected to the world and the community because there was so much more to it than just slaying monsters. I could be happy with a merchant character whose name was featured on gear throughout the server, and whose shop was often marked to recall to.
I may be unique in this, but I think the open, but structured PvP of Dark Age and the customizable classes would blend especially well with the open world and sandbox feel of Ultima Online. I certainly think it could work if you brought back the Faction system from Ultima Online, where there were four distinct factions vying for control of every town. Each faction could be made more distinct aesthetically and provide unique skills to pursue and unique abilities/spells to master like their Dark Age predecessors. However, these factions would be open to joining and leaving by players, and help promote a more neutral group of players that could focus on tradeskills or even provide mercenary-style support to faction battles.
Each faction would provide the leveling curve in the form of ranks and ranking up. There could also be some type of a political game added in where factions have elected leaders and appointed officials in charge of managing precious resources gained from controlling various locations on the map. Faction leaders could help direct players toward specific targets of attack, such as weakened cities, or call for crusades to capture Relics hidden in the dark corners of the world.
I think a blend of the two approaches to character building could also be created. Characters might master specific skills like Ultima Online by doing the action the skill calls for, but each individual skill could be more fine tuned to player's style via points earned from increasing the overall skill. For example, your character may be a Grandmaster Swordsman who gained 100.0 points in Swordsmanship by using his sword effectively over time, but the 50 or so points he gained in increasing his skill so high allowed him to strike a good balance between two-handed and parry with just enough leftover to make sure his one-handed was strong for when he went to his shield. The points spent in tuning your Skill would unlock special abilities and improve specific stats, where as the overall Swordsmanship skill would determine general effectiveness, which weapons can be used, etc.
All in all, I think the two games would make a perfect mix. And as much as the world needs a new Ultima Online, it also needs a new Dark Age of Camelot. Both games are classics in their own right and deserve to once again get some attention. I am not sure that in our world I would want the current Mythic to take over the Ultima Online franchise entirely, but at this point, I will take almost anything.