Not sure whether anyone else has had this problem with the AUR package(s), and this is probably a package maintainer issue (or my local ability to apply AUR repo's properly is lacking, obviously) but I thought this might be interesting for folks who might run into this issue.
I installed the AUR package and it seemed to not copy all the information/files from the package build/source directory to /usr/share/0ad-git/data/ where the program expects it to be. I had to do this manually (cp -rv ./data /usr/share/0ad-git/data) and now the game works smoothly.
If this is irrelevant information for some reason, I apologise.