And yet again a thread mutates into an "anti-cap spam" and "give factions more powers over cap usage" thread.
The whole "cap spam" phenomena is a non-issue. If you see your opponent is cap ship heavy, you bring in 6 bombers and 3-4 fighters. Voila - no more cap ships. It ain't rocket science, people. This game favors the small, elusive bomber (and fighter).
I don't know the particulars of the history behind the creation of Eta. I suspect its chief reason for existence is to be a buffer zone for the Outcasts against the Corsairs and BHG.
In any case, if Eta went poof, Alpha would get more popular.