I am not an expert in Egyptology, but here's my take: For the big, old ones, I'm not sure we'd find much new. There were several purposes for the older, very large pyramids: they were a monument to the pharaohs godly nature and their divine right to rule, they aided pharaoh and others entombed in the passage to the afterlife, and served as propaganda to stand for centuries.

If a pharaoh could not build a lasting tomb, it was a sign of weakness and posed a risk to the pharaohs afterlife. This wasn't a problem in the early period because Egypt was wholly dominant in it's area. Nubia and the surrounding deserts rendered gold, jewels, and stones in untold quantities and the early pharaohs enjoyed this easy abundance of wealth.

The pyramid itself was big on account of it needing to be imposing and monumental, not really for any other purpose. I don't imagine we'd find much additional that we couldnt already with penetrating radar and metal detectors. Grave goods, the sarcophagus, and murals were the most important parts of the entombment. Grave goods, such as figurines, gold, food, clothes, weapons, scepters, were entombed because they were thought to carry over to the afterlife to aid the pharaoh (or whoever was entombed, such as other state officials) on their perilous journey to meet Osiris and spend eternity in the field of reeds. Likewise, the painted murals on the walls of the tomb gave powers and blessings to the pharaoh as well as command of obedience to his ghostly followers. I imagine the wildest find would be evidence of some other variety of these kinds of tomb superstitions.

The newer tombs that had to be built and sealed in secrecy probably would have spent more effort to hide grave goods due to how quickly they might be raided.