I think a DR replacement needs to be more centrally located between Bullfrog and Wahweap, and that means somewhere between Dungeon Canyon and the San Juan. As Lake Bum noted above, proximity to Rainbow Bridge is also a big consideration here, which is why a spot just south of RB would be ideal.
But is there one?
Most of the canyons from DR to Rainbow are narrow and unsuitable for a fuel dock. The square-shaped cove just upstream of RB might work, though haven’t looked at it recently with low water. Otherwise it’s slim pickins… Oak Bay? That would ruin it as a great campsite area. Hidden Passage? Maybe—have to check the width. Or what about Cornerstone Canyon? Again, not as protected as a place like DR…
As for places north of thee San Juan, The road from Hole in the Rock can’t be extended to the lake, unless you’ve got the ingenuity of the San Juan Expedition of 1879-80. Even then, no, that’s not gonna work. The other side near Register Rock works better, but again, this is only about 30+ miles south of Bullfrog, and more than 65 miles from Wahweap… not ideal..
But always interested in good ideas…