I'd love something like nvAlt that has zero hierarchy, but instead offloads to blazing-fast search. The problem with nvAlt is discovery so bolting on some smart filters like LRU, MRU that you can access through commands in the search bar plus a roam-style graph would help you move through the note space.

Then when you open a note, a side panel with back-links opens side by side with the note. Press a key command to flick between the search bar and the note, and update the side-panel whenever a new note is opened. This would be the perfect app for me.