In my humble opinion, I feel that Premium Scrap being removed is a miss-step. Reason being is this could have been evolved a bit to be used to produce some of these high value items such as Manifolds (higher yield repair material sold at Junker stations) or other higher yield items. Maybe I'm biased as a Junker player, but that's how I see it.
What are the repurposed ores being used for? You mention Military Salvage and Xeno Relics as an example. Where will these be going and what will they be used for? Unless I missed that in the post.
I'm reserving my skepticism until patch release but I'm cautiously optimistic that this will be an interesting change. Making it more player involved is a step in the right direction and allowing scrap to be mined everywhere inside the corresponding field(s) (as it should) is a good idea. My Junker is gonna be busy.