I guess I'd like to see the first of Enterprise's relaunch novels - "The Good That Men Do", done like that. Plenty of reference material that exists to render in traditional 2-D cells or 3-D computer generated figures. Actors all still around to provide the voices.
As an animation, it still wouldn't be considered canon but it would be a heck of a lot better than "These are the Voyages..." and end with the Romulans' first strike against the Coalition. So pointing at what was actually supposed to have happened next, whether further cartoon feature-films would be justified or not. If by some miracle they were, with the major stumbling block of undoing Trip's death dealt with, then they'd perhaps have to be more loosely based on the following books depicting the Romulan War.
The other possibility that has always occurred to me, is presenting the first two Shatner books - Ashes of Eden and The Return as lost Star Trek movies set between VI and/after Generations.