I have pieces from almost every current artist and just completed my ESB Fett and am awaiting 501 approval. First off, you have to ask yourself "Why?" do I want approval. When you build a Fett, you are buidling it for you. You will think one piece is better than another. Taste, fit, budget, your own interpretation of screen accurate will ultimately determine your final vision. But there is no one artist or prop maker that has it all. As they strive to do so, it only makes our end product better. For example, my soft pieces alone have 4 different sources. I'm currently making a custom set of gaunts with three artists pieces, and after celebration, I'm rethinking my whole EE3 set up.
But as soon as you get 501st certified, it won't be over. The upgrading, the research, the adjusting... it won't cease.
I have MOW Neck seal, boots and ammo belt. I will be upgrading the ammo belt however. No Bobamaker yet but I will have at least ROTJ SE Armor.