I think one of the reasons for the dislike of low air mobility in games (compared to real life), is because a crucial information is missing.
In real life we can see our feet in our peripheral vision, this allows our brain (unconsciously) to sync up our feet with a target line or ledge on the ground. To confirm this I did an experiement: I blocked my downwards peripherals with my hands, and it made me much less accurate at hitting and jumping from a line on the ground.

So to solve this I propose an indicator for whether or not the player is currently on the ground. Together with coyote time and coyote frictions (see #1969 (comment)), this should be enough to give the player some time to react when stepping of a block.
As for how that would look, I propose just a small horizontal bar below the crosshair that gets toggled on or off.