I don't yet know if there will be any semblance of crafting incorporated into the game. But, presuming it was possible to implement and it didn't break lore too badly, would you want to see crafting in the game or not?
Crafting but not gathering, crafting should be focus on customization of weapons and so not build itm x,y, and pls DO not add same strange weapons WH40k universe have as many weapons do you want
In the 40k universe there is no time for Mat Collecting for there is only war! Every PC in this game is a soldier and they should be doing what soldiers do -fighting, its not a survivalist game where you need to make potions or necklace's in the safety of your Chapter House for the next tear of equipment. There should be no 'barter house' for Space Marines to sell that super rare helmet they got off a Boar they grinded for hours on in No Mans Land. Your a small cog in a big war that requires you to fight, not pillage a forest for blackberries, or collect squig teeth in a cave for a ring that gives you +1 to your absolution, or the mats to make one. If your standing around doing nothing, your either talking to your allies or your waiting peevishly (or with fear) for the next assault on or against something. Go with a trophy system. The more you kill, the more you explore, the more bases you pillage or missions you go on you get a trophy that can be put somewhere on your armor. You find some Easter egg? You get a trophy. You kill 1000 people in pvp? You get a trophy. You slaughter 10,000 grots with grenades? Dang-it! You get a trophy.
You know how Ork war-bosses collect the heads of important enemies... you can have a trophy rack on your back. Exactly like in the games. Space Marines could maybe have a dangling Tyranid head or some claws. Chaos Marines have something similar to Orkz. Eldar... I got nothing for Eldar.