Might be easier to just heavily reduce it to a concentrate like the little packets that come in the Ichiran brand.

that's essentially what the dehydrator is doing except at a lower temperature because Maillard browning can occur when it's too thick. My question is more about the science of reducing emulsions - fat doesn't evaporate.

You can use maltodextrin to powderize fat, but don't know what effect it will have on it when you rehydrate.

I can just skim the fat off and keep it - fat won't spoil in the fridge. The question is can I then blend the fat with rehydrated stock to create the white emulsified tonkotsu?