I just thought I'd update and mention that the GiantsWD folks are working on an unofficial 1.5 patch which is close to finished. It includes bug fixes, gameplay balance changes, graphical improvements and a bunch of other stuff. It seems to supercede and make obsolete some of the older mods mentioned at the start of the thread. I haven't tried it yet, but it sounds great.
I'll end with one of my many GOG suggestions that probably won't be done, but: When the patch is done, it would be interesting to have both the 1.4 patched version (the last official patch) and the 1.5 (unofficial, but theoretically better) versions of the game. This game is so glitchy that the latter might be better for everyone.
Final change list here: http://www.giantswd.org/forum/viewtopic.php?t=1962
Discussion thread here: http://www.giantswd.org/forum/viewtopic.php?t=1888