Your setup sounds awesome, I'm envious! Coco can definitely be reused, there are some good threads on it here somewhere. I've reused it three times max, was scared to try a 4th, and there was not much difference between grows. I use organic base nutes, but add some salt based ferts during bloom, so honestly, I'm not sure if 100% salt based ferts all the way through would build up more. I also use enzyme products to hopefully break down some roots, but truthfully, I think they don't matter. When I'm done with a batch of coco, it goes straight into my outdoor garden-wonderful stuff.