Yes IK solvers can work very well even to customize animations, like getting a zombi walk from a usual walking mocap, but I think an approach using heuristic optimization and a basic anatomy model can go well further and is more generic, for exemple you could add dexterity (e.g the character may fall) and energy constraints (e.g tiredness). As for use in real time it may be becoming possible with high end gaming PCs, that is something that would be interesting to investigate, also cloud gaming is becoming more and more mainstream. But even offline it would be interesting, you could record the logs in bone transforms of the functional animation you obtain and place it in a keyframed animation. Unfortunately, I didn’t see yet any people out there working on procedural animation^^’
edit: kof kof I just saw this Creature - 2D Procedural Bone + Mesh Animation Tool with UE4 Support released! - Character & Animation - Epic Developer Community Forums, it looks very cool but it is for 2D