i thought unity3D used too much space. if space is a big issue i think godot is pretty tiny compared to the other two engines though it's a little weird but it does have C# support by default. it's cool you're gonna add new stuff though i hope you don't overwork yourself and personally i'd stay away from unreal. they don't even want people being able to call some a nuke in games made in their engine. it's bizzare.