The difficulty with ATNotts proposed solution is that opening up the UK borders to EEA arrivals in the same way as if it were part of Schengen, or indeed joining Schengen, would cause huge problems in respect of people already illegally in Schengen. They will now find the gateway to the UK open as well as the Schengen countries.
This is what the UKBA/BF wants to guard against - they are doing an appalling job whichever way you look at it, but opening the borders would be a retrograde step.
I don't pretend to know what the solution is, but then I'm not paid hundreds of thousands of pounds a year to do so!