While we don't have near the high end bikes you have, we had a similar situation. When we bought our PU it had a cap on it. Its only a short bed. In the past we hauled our bikes in our trailer but our new trailer has a couch and we didn't want to chance damaging that. So the PU bed seemed an ideal way to haul the bikes.
Anyway I played with the idea of a fork mount system like you did with your Escape. I really found it clunky to put the bikes in and out with height limit of the cap. And honestly, we only have 3 bikes but that takes up more of the bed than you might think. I can't imagine trying to do this with 6 bikes under a cap.
Ultimately we sold the cap and got a solid panel folding tonneau cover. We remove it and put the bikes in using a home made rack. I know that won't work for you, but I don't think you'll like the truck cap either.
Given your need to be able to work on the bikes in a dry location I think a toy hauler is your best bet.