Hello! I was recently exploring modding of this game and wanted to offer a way to make the patch better. As far as I understand the patch repackages .REZ archives to make the changes.
What I suggest to do is to instead of repackaging .REZ files you can just recreate the directory structure inside the data folder and put the files there. Lithtech prioritizes files there by default. That way there's no need for installer since you can just merge the files with the data folder.
As I understand while the game is in development this is the main way for it to get the resources. Only after release they are being packaged into REZ files to reduce the size.
That also simplifies the removal of the patch since you can just remove the files the patch added, without altering the main REZ archives.