I would think that at least keeping the automated gates available for British Citizens would be efficient.

Interestingly, I have noticed that the e-passport gates are somewhat under-utilized by non-UK citizens. I took a flight a few months ago from CDG to EDI. The Brits all had their passports and proceeded to the automatic gates. The French for the most part were travelling with ID cards As i understand it, the Brits don't have ID cards so basically must take their passports for travel within the EU.