During a round of running around on Google tonight, I found something new to me: a retrospective look at the original Phantasy Star, including a 2003 interview with Rieko Kodama.
http://sega.jp/archive/album/07_ps/
Here's a link to the Google automatic translation:
http://64.233.179.104/translate_c?hl=en ... bum/07_ps/
The first page doesn't translate because it's all images, but the other pages do. The translation isn't the best, but there are a few interesting tidbits in it. For instance, it explains the switching of Motavia and Palma in PSII by saying Motavia takes a long time to orbit the sun and crosses orbits naturally with Palma. That's a complete contradiction to the explanation we've had before from the PS Compendium book, which says the planets switched orbits in a massive disaster.