Whenever I open the game to see credits or blueprints as mission rewards I die a little inside.
I know some people, especially on this reddit, really adore having blueprints but when you a) have already grinded through the most painful tanks there are and b) slowly moving up the tech tree is part of the fun, you amass an amount of BPs that you won't be able to spend – usually there is just the low tiers and one real turd that you have to skip (TVP VTU, AMX 65t, Sturer Emil, Churchill VII etc.) – that is unless you play Chinese tanks which I hear are mostly terrible with few exceptions.
Getting 50, 30, 20 or 10k credits as a reward is frankly underwhelming as well since all it takes is one okay game in a premium vehicle to make that amount – or two in regular T5-T7 tanks.
Recently I often get the same reward when I reroll the daily mission – but with another mission. WG seems to think that that is the case because the mission is "too hard" but usually the missions can be done all in one game or they just take some form of small grind (the pain when you get 4k Base XP, 4 wins and the likes for something like 50k credits though – obviously on the bonus mission which you cannot reroll anyway).
Thus it would be great if one was able to block one reward type for free and two with premium – a bit like the map blocking feature.
My ranking would be the following: Crewbooks, Bonds, Demount Kits, Free XP, Credits, Blueprints so that I could remove the last or the last two depending on my account status.