It seems like a lot of folks don't like having to complete ALL the episode-related content IN ORDER, especially considering the rewards for a lot of the early missions don't currently correspond correctly to the level you are at.
So my suggestion for the dev's is this:
Open up one of the episode groups at each tier.
For example, you start with the Klingon missions you have to complete in order. BUT when you hit level 11, the Breen missions open up, and then level 21, the Romulan episode arc, and 31, the Cardassian arc, and so on...
This will allow a bit more "freedom" while playing the game, along with keeping everything nice and tidy in a sequence in terms of the episode content.