I'd certainly like that option, especially if a lounge opens after pre-clearance.
Should of guessed you would! A lounge will open in a few months.
It strikes me that it should be possible; simply put one-way doors on the entrance to pre-clearance from within the existing departure lounge, then build an enclosed route through one corner of the building.
Building such a route is not practical and never going to happen. If they don't want to do security twice find an alternative routing.