This is actually my main concern. Changing the low res interiors to high res in the cockpit alone is one thing. But being confined in just the cockpit/bridge will be a letdown for everyone who has been waiting to walk around their ship. If FDev really wants to make Legs cool, they will have to add more interior to all the ships. A personal chambers, the cargo bay, the hanger, passenger cabins, engine room, etc. All that added stuff will cause more instancing issues. Instead of just loading in the cockpit, hardpoints, modules and exteriors of each ship that comes into instance, all these interiors will have to be loaded into every instance as well. They could do something like a "loading screen" while you were docked or landed on a planetary body, then you would be warped into a different instance where the whole interior existed (as it would otherwise not exist in "normal" instancing), but I really don't know if that would work in the current peer-to-peer model.
Sure, a top o' the line pc might be able to handle this, but your basic gaming rig or console? We can barely handle multiple players in one instance as it is....
EDIT: Btw, props for Lydia. Better looking Lydia is better looking. I just don't like the mods that change her personality and take away her snark.