(most of the credit here goes to mitjitsu)

There is a glitch to get 9,999,999 dyne at the beginning of the game by using a Panzer Dragoon 2: Zwei save file. It requires the PDZ save file to have 199 hours logged on it. Mine has 199:00 exactly. I achieved this by idling on the Zero Space mission which does not make the disc spin, allowing me to leave it on overnight. I also copied my save frequently to a memory card so as not to accidentally go over 199 hours exactly. There may be some wiggle room with the exact amount of time needed, but 199:00 does work.

When you start up PDS, you'll have -19868 dyne (or close to it). The important part here is the fact that it's a negative amount. After you gain a small amount of dyne with the first encounter, you'll then have 9,999,999 dyne, which is the max allowed by the game.

The game doesn't expect this number to ever be negative, so when it checks to make sure you don't have more than the max, it does an unsigned comparison. This treats your negative amount of dyne as a number much larger than the max amount, so the game hard sets your current dyne amount to the max.

To 100% verify this is happening, I suspect disassembling the game would be required, which I am not willing to do. But I am happily able to verify that early max dyne can be achieved with only a copy of PDZ and PDS.