My project Lokalized attempts to solve many of these complex plural/gender/ordinal/etc. rules with a tiny expression language:
Same here (linked to a test because I don’t have a (meaningful) readme…)
That being said your project looks very cool!
https://github.com/Frizlab/XibLoc/blob/e85a5179bdd93e0174731...
Are there any formal test suites to check and compare the various localization libraries with each other? There's a lot of languages and language specific rules and exceptions to consider, after all.