So… now i am from the Federation, but i still can buy ships and acquire “Missions” frrom the Empire, is this supposed to happen ?
Sure this is normal. You can get a higher rank in every faction.
i think that this kinda “kill” the role-play xP (it will turn the game in a big Arcade)
Well at the moment the game is planned to be PvP based so most players will want to test every faction and find good combinations.
hmm… it makes some sense now 
(BTW… when will be an english changelog for the last update? 27/07 )
A fixed faction would be more for an open world game with a story.
The Patchlog is already translated. You can find it in the Generel Section.