I actually really like the idea of having the feeling that you are working towards something and I believe this is a viable system. Getting 5-10 tokens would be reasonably hard to do and it would make looting duplicate exotics not completely useless (especially when they give you the same amount of ascended materials as legendaries when dismantled). Happened to me the other day when I looted a Gjallahorn from an engram and the next day got it from a chest in the raid, I mean it's cool that I got an exotic but the same damn one that I can't do anything with? I think that there would have to be 2 sets of tokens, one for armours and one for weapons but other than that there is no reason why this wouldn't work/shouldn't be implemented.