>>725162415
It is entirely feasible. Look up Dialogic, it's a dialogue system plugin for Godot that will trivialize the VN portion of your game, but is still really customizable. Plus, a bullet-hell is incredibly easy to make. Low art scope, easy programming, etc.
Godot can handle both easily.
Will it be fun? Hard to say, but I think there's a point in your favor that VN enjoyers and Bullet Hell enjoyers have a lot of overlap.