So this is mod idea, but not for CIU.
Long time ago I found the website of people who worked on CI3 music.
I’ve also checked that these guys also made music for other games such as Moonhaven soundtrack for Super Monkey Ball Adventure.
I think it will be very generous if there could exist such mod which swaps CI3 music with the ones composed for other games
EDIT: If you don’t know what I mean, then compare tracks 18 to 24 from said game:
to the music in CI3:
Or even to this one: