Well, I did that. That fixed the most of the problems with the Army of the Light mod (and this is why some of the screens from it are in english), but one crucial remains - no pictures show for the Mage of the Light's gift and heal abilitites whatsoever, which leads to a crash. I made my own pics (by editing and renaming the original pics to suit the game), but that forced the game to show empty buttons. Well, at least it stopped crashing
As for the Army of the Dark, it causes a duplicate file hash for the dryad (a window will show, and if you hit ignore, the game simply continues), but it has a built-in enligsh translation. It's a bit poor, but it is understandable.
In the master mod (required to run these 2 versions properly), one should translate parts of the loc files to fix all the NF errors. Actually, the only NF error I found was when trying to bring up the info about the master mod, so it's not that big of a deal.
EDIT: Well, I managed to fix most of the army of darkness errors and corrected some improper translations in the localization file. There are still a few missing button pics though, but at least now the game starts without any warnings about duplicate file hashes.