Well I agree 100% with you !
However, there is a hardware limitation that is that if the CD-ROM is used to stream audio data, it cannot be used for anything else. Since Dragon Quest uses sequenced music all the time (even during movies !) it probably uses the CD-ROM for something else most of the time.
So you have two options :
1) Hack the game so that it only loads data when music is not playing, and it stops music when it has to load data (I have no idea if this is possible
2) Hack the game to use an intelligent streaming system like Grandia, which allows to load several seconds of streamed music in RAM, and put other data loads in-between the regular music stream loads.
Also, you have the problem that CD-ROMs are limited to about 650MB of data, and I don't know how much of it DW7 uses.