Yeah adfly, I tend to agree. EWR seems the best option for a second service. A twice daily service seems feasible and it would give much better and more flexible timings on the route if they could say, get a morning departure from LTN to complement the existing early evening one.
As you say, a very competitive market - even somewhere like IAD has tough competition. Fingers crossed for them. The early signs weren't good but hopefully they are upping their game now.