I think I've discovered what causes this error, RK. Almost by accident.
As of my last post, I extracted the .2da file from biff to check its size so it was now residing in the same folder as the weidu .exe. The next time I tried to install the sample kit, I successfully replicated your error.
Basically, the problem lies with weidu checking the wrong file - instead of using the successfuly patched kitlist.2da file in the override folder, it's looking for your kit_name in the file you have in the folder with your installer's .exe file. Delete or move this file, and the problem should go away.
This is because of how this check in the .TPA is processed by WeiDU:
PRINT "Doing EE-type kit extensions for kit %kit_name%"
ACTION_IF "%kit_name%" STRING_EQUAL "" OR
NOT FILE_CONTAINS_EVALUATED (kitlist.2da "%kit_name%")
BEGIN
FAIL ~The variable kit_name is required to name a valid kit~
END
FILE_CONTAINS_EVALUATED will try to load the specified file (kitlist.2da) from several possible locations in this order:
1. Inlined files.
2. Specified file path (no path specified = current folder)
3. Override folder.
4. Biff files.
In your case, it was finding #2 before getting to #3.
For Wysp: I don't know if this qualifies as a bug or something that should be fixed, but this can be easily foolproofed against by changing the check to this instead:
PRINT "Doing EE-type kit extensions for kit %kit_name%"
COPY_EXISTING kitlist.2da ~override~
ACTION_IF "%kit_name%" STRING_EQUAL "" OR
NOT FILE_CONTAINS_EVALUATED (~override\kitlist.2da~ "%kit_name%")
BEGIN
FAIL ~The variable kit_name is required to name a valid kit~
END