The rez thing should NOT be used. it is for legacy stuff (classic apps)
It's much better to build an app bundle. Quick example of how to do it:
Target > Build Options > Pre/post build steps
Pre-build steps:
mkdir -p $(TARGET_OUTPUT_DIR)/MyApp.app/Contents/MacOS
mkdir -p $(TARGET_OUTPUT_DIR)/MyApp.app/Contents/Resources
post-build step:
cp $(TARGET_OUTPUT_FILE) $(TARGET_OUTPUT_DIR)/MyApp.app/Contents/MacOS
This is dirty and incomplete, but if you continue in that direction, add an info.plist file, fix executable location instead of copying it, etc. you can probably get it working quite well enough
If you can make a wizard out of that, please share it, it would be awesome