On one of the interviews the developer had said that you can turn certain options on and off to make the game more harder or easier for you from the options menu. You can even turn the "Instinct Mode" on or off as well which is an ability similar to Assassins Creeds "eagle eye mode". So I'm sure you can adjust the difficulty level to your liking in many ways. Hope this helped :)
Havn't heard anything about customizing weapons yet but that would be awesome if they left that feature in the game.