Is there an easy way to create logical links to be added to a new build under the openwrt/files/ folder?
You don't need
uci-defaults, you should be able to symlink in the ./files directory directly to where it needs to point to on the device. Remember that
./files/ get's copied to the image root.
You could, in
./files, do a
ln -s to where it would be on the device and it'll copy the link-file over with the rest.
ln -s /usr/bin/something /usr/bin/symlinktarget inside the
./files directory structure.