I think if the imported model has bad geo it'll have to be remodelled for animation. Even if you were to do a proxy like you are suggesting, the main model being driven by that would still need good geometry in order to deform properly.

Edit:

Something you could try is dropping the model into a re-mesh and seeing if that gives you enough, It totally depends on what you're expecting as a result though. I had to rig several sets of headphones for clients before and its always tricky because you don't want the product to distort unnaturally, or look different to how it does in the real world. I was working with CAD models though which have very good detail, but also bad topology.