I'm going for Platinum in Wolfenstein: The New Order. All that's left is the Uber Hero trophy (beat the game on Uber). Can I start my run through the chapter select menu, thereby keeping all the upgrades I've already earned?
To get the achievement/trophy for completing the game on Uber, all you need to do is select the last chapter (Chapter 16) from any of the two timelines and go through it. Both this achievement and Super hero achievement will unlock simultaneously (assuming you completed the campaign on normal or a lesser difficulty).
You will also keep all the upgrades you've earned so far.
I have also gained both achievements by using the chapter select.
Here is a rough guide for the boss fight