I can see where you coming from but i'm not sure if anyone would try and offer it, it would be nice if BE or RE tried to offer it but sure that they won't until the 3 year deal has ended with the Highland if they descide not to operate it anymore.
I think there maybe more of a chance that there would be a CWL - IOM - DUB route than the CWL - VLY - DUB. There are airlines looking into VLY apparently but i would say it would be one of them linking with CWL and onwards not any other.
I was wondering how a VLY - CWL - (London Aiport) would do?
I'm not sure Ryanair would base at CWL uness they pulled out of BRS.