This reminds me of the WH40k: The Inquistion novellas. Inquisitors tend to have, as you word it, some "idiot savant" data-addict attached to their group. They come with a photographic memory and a craving for knowledge of any kind, lore-wise caused by a virus. It's a cool concept and might offer you all the immersion you seem so keen to get, while also allowing for a journal that still has remarks on anything. Since it's in your savant's photographic memory, there's not even a reason to take a rest in order to write it down.
Example: http://wh40k.lexican...wiki/Uber_Aemos
oh, and as they tend to get unbelievably ancient, their limbs would be replaced by augmentic (cyborg) body parts, eventually enabling them some serious combat prowess
