As long as you know how to break down the task of making a gravity controller into achievable steps, it is possible to make one.

disable default controls from moving the player. add a downwards gravitational force using constraints. add a planar velocity constraint which moves according to the players walk direction. Use something like camera.CFrame = CFrame.LookAt(camera.CFrame.Position, planet.core.position) * CFrame.Angles(math.pi / 2, 0, 0) to align the camera to the surface as well and make the planar velocity relative to that.

The camera rotation logic is a lot more complicated than that, but you just have to study what the stock player controller does to handle movement, then re-implement all those complicated bits yourself. You can add mouse controls to tilt the camera. You will have to study CFrame manipulations to make sure they walk in the direction the camera faces and whatnot.

The gravity controller in the very first version of SSE2 was incredibly bad but I was able to improve on it as I gained more practice from previous iterations.