A server transfer from NA-EU and EU-NA respectively as a lot more difficult than moving from NA-Brazil or to another server. Riot would more likely not have this feature into the game because these two types of servers are servers that already house alot of accounts and connections, this is a (kinda) good way to keep the balances between servers since if riot had implemented these types of transfers, people would all shift to one server which would not serve Riots financial interests.
Plus most Riot staff are preoccupied with various activities revolving around the game so if you want it to happen you would have to wait until the start of Season 3, who knows? Maybe they might implement it then? 