One minor (optional) tweak to the PRV grid is all it would take to push me over to upgrade from X3. I would like to see a music-staff style grid under the notes in the PRV. The spacing would be constant (i.e. no extra space between staves like in regular sheet music) and the ledger line between staves would be dashed instead of solid (maybe red dashed for middle C). The note blobs could be on the line or in the space, but would still be regular note blobs just like in the current PRV. If any of this is confusing please let me know and I'll try and mock up an image.

Interesting. Is the goal to edit in PRV and see the result in staff view that is locked horizontally to along the PRV view?   Perhaps similar to sequencer view in Notion or midi/score editing in Pro Tools.

I'd say the goal is to have a PRV where I can look at the lines and intuitively know what note I'm looking at. The slowest part of using the PRV for data entry (which I do when I'm writing parts, for instance) is having to track back to the left side of the screen constantly to figure out what line is what note. I first encountered the sort of thing I'm looking for on my first DAW, the budget PowerTracks Pro Audio, which I used for a few years before graduating to Sonar. Anther time this intuitive workflow comes in handy is when I'm cleaning up a MIDI performance and have to adjacent notes. If I know which one is correct just by looking at the screen, they saves time over having to play each note to know which is the right one.
 
Thanks for the interest.