Why not dump all of our nuclear waste there? Shedding orbital velocity. Eros the magic space potato.
Our lack of understanding irl of whether humans can conceive and gestate and grow in low or microgravity. Centrifugal artificial gravity.
Pulling Gs. Human limits.
Finally we’re in a place that we’re taking space settlement for granted. Developments in space travel like the Falcon Heavy et al. Recently, Stratolaunch:
Fragility of interconnected systems at small scale. Radiation. Living inside a big rock.
Venus sucks. Mostly. On the surface, at least. Soviet Venus missions. Turning Venus into a spaceship.
Harvesting and limiting solar exposure in different parts of the solar system. Relative solar intensity.