As it happens, Gemskip is entirely possible. Unfortunately, the berry in the same room as the chest is impossible in Gemskip, so I am left to mourn with my imperfect score.
This mod was very fun, and it's also quite faithful to how the mechanics work in Celeste. The chiptune mixes of the songs were also a welcome touch. My only real critique is the one berry that isn't possible in Gemskip, though such a route was never really intended to begin with.