Is it absolutely necessary to have separate directories for playing both EU/US or be forced to manually rename and patch them every time you want to switch EU<->US?

I really hope this is something that will be addressed before launch because if this by design it seems rather short sighted on Zenimax's part and very annoying for players who plan to play both. Because even without knowing the internal workings of the ESO client I am willing to bet that over 90% of the data is the same both for EU and US.

the most problematical issue about it is the launcher is deleting the foulders quite randomly (if you have both clients installed) and starts to download the region entirly oncemore wich really suggs

I thought this had been addressed? Come on ZOS, please, there's no reason to have two file directories - no other mmo I've played has this.