I see little point in an EasyJet premium section, apart from the obvious piece of adding complexity to the model, they don't need to have it to collect higher fares, they charge a fortune on the last tickets per flight, in their successful yield management approach.
They have very good facilities for those who want fast track etc...easyJet plus is great value for me, adding a premium service would simply look like a seat closed off in the middle and an increase in price of at least 50%.
Let's also not forget a high proportion of easyJet flights are quite short ie 1-2 hours...