Are there 50 people a day who would be prepared to pay for an early arrival into London? Probably
Is there anything else that could profitably be done with an aircraft of that size? Probably Not
At the moment, London has less capacity than it did even before the Easyjet/Ryanair battle on the Gatwick route. Of course, the upside of that is that Aer Lingus and Ryanair are getting healthy yields on the Cork-London route.
The best bet for a properly early service to London would probably be if Aer Lingus did decide to launch a Gatwick service. But there's no sign of them expanding anywhere at the moment, never mind in Cork, so that's only going to happen by cutting other routes and I don't think any of us really wants to see that.