Tom
As you will know the charter market has being in decline as many carriers have gone bust over the last number of years and its becoming difficult to source such carriers. Then there is the cost side of contracting such operators balancing it with what the public would be and scheduled carriers like FR at ORK.
The airline you suggest only operate from PMI mainly and positing an aircraft to LPA and back to operate ORK just wouldn't be viable.
DUB-LPA has operator TBA but suspect its the reason however there is the possibility they have temporally removed ORK-LPA to see if they can find an operator.