Good resource management is the cornerstone for any good RTS I've ever heard of. The only reason your resources begin to "boom" as you head into the mid-game is because you've probably chosen planets with a good amount of minerals on them, strategically, as they are of great value to you. Just as Chris very elegantly pointed out, every phase of the game is different. If you could just start out the game pumping out everything you wanted, how would the beginning of the game be any different than a basically easier version of the mid-game?
When you choose to unlock upgraded harvesters first, you are making a knowledge sacrifice early on that could have been used on something else. From my experience, the way you use your first 10,000 Knowledge is vital on the higher difficulties, and can make the difference between winning and losing. Your suggestion almost nullifies that strategical aspect of the game, and of the early game in general. When I watch Suzera play, she simply chooses what she wants at the start and ups the speed until she has everything she needs for her first/second/subsequent attacks. If you find the early game too slow and tedious, I would make this suggestion to you as well.