As your are reimplementing the viewer in IMatch2023:
I would love to see a floating film strip (or better: grid).
Thus one can move it to a secondary monitor and use the primary monitor full frame.
(Similar to FastRawViewer and/or Lightroom)
I don't make any changes on the Viewer, except for the smart menu.
Since you can move the Viewer window to a second monitor and use the entire File Windows as a film strip (press Enter to load all files into the Viewer and focus on the focused file) I wonder what a free floating film strip in an extra window would do in addition.