No need to imagine. That kind of hybrid is frequently used in modern anime, though it's getting less and less visible with time. These days it's basically only apparent with low-budget productions, or by looking for scenes that are animated too smoothly and consistently.
One of the major determining factors of if CG blends well with 2D animation is if the 3D was farmed out to another studio or done in-house. All of the biggest 2D-3D hybrid success stories in anime (such a ufotable, the studio behind Demon Slayer) have an in-house CG team that works in tandem with the 2D and compositing teams.
