Many game engines have these. What are we going to do for ours? I don't think we need to work on this right now, but we should cook up some ideas:
Should not be forced on the user to make a game. It's completely fine to make a game without one, though recommended. I really don't like engines that force scene graphs onto the programmer.
Engines like Urho have serialization/deserialization for their scene graphs. Might be nice to have for ours.
I think this is a plus (or kinda necessary) if we want to have a level editing tool.
I agree we should eventually add one. I haven't looked at Urho3d's but I have looked at Horde3d's and I like theirs. Maybe we can steal ideas from both. Either way I agree with all three of your points.
Many game engines have these. What are we going to do for ours? I don't think we need to work on this right now, but we should cook up some ideas: