I have similar requirements. In my opinion, Away3D is not yet ready for 2D use. Sprite3D is fine, but there is no texture animation built into it yet, nor is there texture atlases/tools in the engine.
If you have immediate needs, I would research NV3D http://www.nulldesign.de/, which has its roots in Cocos2D. I have not looked at it myself yet, but if its as close to Cocos2D as it claims, it is probably a very good starting point. -Dave
