I can recall when Ultima 9 was originally conceived it was anticipated to be isometric 3D RPG. Here is a screenshot http://i.imgur.com/MGDSXYP.jp . Voxels would seem to be a great fit for such an engine.
Hopefully in the afterlife I'll be able to play U7 again for the first time. What a great game and a hard act to follow.
using game data from older games sounds like a great idea (if any of those licenses allowed it)