I haven't looked into it in too much detail, but the fact the only way back into AE is via image sequences sounds like a show stopper for me.
DUIK is quite a different thing. It's a script UI Panel that assists in the rigging of IK characters, amongst other things. Compared to 3D or 2D software tools designed for native character animation, it's quite a cumbersome workflow. But if you have the patience and skill, you can achieve some quite nice results, and you get to keep everything in After Effects with all it's other tools, integration and whatnot. There are other IK rigging scripts for AE but DUIK is the most full-featured.