Good conversation. I'll play along.
From a kayaker, and user fee perspective, the current ramp is adequate... but, you posted this in the rafter forum, and the boat ramp is pretty weak given the amount of (large/heavy) raft traffic for that section of river.
Given the current operation of Reservoir Powell, your points are all valid, which brings up the larger conversation of how to manage Reservoir Powell and other reservoirs on the Colorado River.
If we (as society as a whole) agreed Powell would likely never be filled again, or shouldn't, then it may be a great investment to redo the boat ramps. There is already talk of draining Reservoir Powell to fill Reservoir Mead, and perhaps the new status quo would become to keep Mead as full as possible, and Powell less so. There are many pros to this, limiting evaporation loss at the top of the list. Permanently lowering the maximum elevation level in Powell (designating full pool status at an elevation below the takeout) would solve issue #1, and to some extent issue #3.
As for issue #2, I figure if the silt build up remains dry for long enough, then a primitive (dirt/gravel) boat ramp would work okay.
Multiple reservoir expansion projects are underway in Colorado, so what little water we have naturally, we are capturing closer to the bulk of our populations (or more likely, pumping from the Colorado drainage headwaters east to the metro areas). The likelihood of Powell ever reaching it's historical full pool level seems slim as our population and water demand increases throughout the western US.
Curious as to others thoughts.