All text files have been already found.
There are single text files in the game, and WAD/IDX pairs containing texts. The WAD/IDX pairs are discussed in WAD/IDX section, so here I will focus on single text files.
There are two such files: PEOPLE.TXT is used for displaying ending credits, and TEXT.DAT contains names (weapons, mods, agents) and messages (interface, errors) from the game.
The texts from EXE files are also extracted, you can download them here:
Download Syndicate Wars Texts extracted from EXE
Reworked! text files:
PEOPLE.TXT TEXT.DAT