Perhaps a possibility would be to combine multiple tracks into one mp3 so that each category would play more than one song...the biggest problem I can see is the majority of those are high tempo battle themes...it might be wise to try to mix in some soft, subtle music, so that it plays one, fades out for a little bit, then switches to a different song. I think I know of a program that can do that...but it's your call whether you think it's worth incorporating. FFXI has a lot of music that would sound nice, say, for a diplomacy screen...
Here's music I think would be a good choice, although admittedly it does rely a little heavily on FFXI music. I think that each reflects the culture group accurately at that point in time, rather than based on story progression, but I realize you already have a full track list, so I can understand if you'd prefer to stick with that one...
AncMEFull -> Guadosalam, X-2
AncGRFull -> Batallia Downs, XI
AncECFull -> Tipa, CC
AncORFull -> The Greatest Warrior, VII
AncNAFull -> Cosmo Canyon, VII
MidMEFull -> Rabao, XI
MidGRFull -> Backborn Story, T
MidECFull -> The Castle, VIII
MidORFull -> Windhurst, XI
MidNAFull -> Selbina, XI
IndMEFull -> Mt. Gagazet, X-2
IndGRFull -> Matoya's Cave, Black Mages Mix
IndECFull -> Bastok, XI
IndORFull -> Black Mage Village, IX
TechnoMixFull -> Regeneracy, XI
StarsFull -> Silence and Motion, VIII
SmashFull -> Battle with Seymour, X
NightengaleFull -> Airship Medley, VII, VIII, IX, and XI
ModernFull -> Still More Fighting, VII
Now, to explain a bit further about these songs...the ancient ones seem pretty self explanitory. The Greatest Warrior shares the tune of Cosmo Canyon, but has a more Asian sounding style. Cosmo Canyon's Native American style made it perfect for America in the Ancient age.
In the Middle Ages, the reason Selbina is chosen for American civilizations is because it's reminiscent of music associated with the first European colonizations of America. Although this does not relate directly to any Final Fantasy storyline, neither was there a Final Fantasy game reflecting American colonization, the most logical choice given the themes available.
As for Backborn Story, I'm really not too attached to the minute long piece from Tactics...my brother recommended it for me, so I put it in. If you have a more logical concept, don't hesitate to bring it up.
In the Industrial age, Black Mage Village is still used, but for the Asian culture group, which it better relates to (Windhurst and the Forbidden Lands both seem well summed up by the piece...). Battle with Seymour, which sounds decidedly Modern, probably should also be placed in the modern music. As for Matoya's Cave, I admittedly do find that to be somewhat difficult to grasp, but it represents the union of medieval concepts and modern technologies that define the civilizations in the culture group. Please note that despite the song is performed by the Black Mages, it is actually fairly tame.
For TechnoMixFull, while it does say "Regeneracy, XI", this is merely the most up to date version of the Prelude, not an attempt to change the song. Silence and Motion, as you probably don't know, is the theme for Esthar, and among the most underrated songs in Final Fantasy. Played for about 5 minutes in FFVIII, it sounds very modern, and it works well in the Civ III dynamic by shifting between a peaceful sound and an intense warlike one.
The biggest problem might be Airship Medley - the idea is to take the music from Highwind Takes to the Skies, Ride On (FFVIII), Hilda Garde III (FFIX), and Airship (FFXI), and play them end to end in one mp3. This solution would please Final Fantasy players who have their favorite games, but at a running length of approximately 12:30, it might dwarf the other Modern songs in its length.
I'm aware that you feel very passionately for One Winged Angel, but, sadly, it would most likely be far too distracting...
I'll put in a Zip file with the tracks listed on this post in my next post.
)
It was one of the nicest surprises I found in the FF series 
