You had me at TheBrain. Even if as a bare minimum, this plugin could create nodes from notes (auto suggesting names like wiki links do) and allow child/parent/sibling hierarchies, it would be so wonderful!
I understand that there could be performance issues if someone actually uses it like TheBrain with hundreds of nodes. But I think that could be solved by creating many maps which act as views in TheBrain ie when you click on parent, you see a different map of it’s own child/parent/siblings but since it’s a separate map it wouldn’t need to be loading all the nodes from the previous ones, only one link back to it.
Good luck!