Have you tried Hydrogen connected to Ardour via JACK? AFAIK, it would give you everything you described. I’ve used it a handful of times for drums and been very happy. These days I prefer https://x42-plugins.com/x42/x42-avldrums and play in with a MIDI keyboard.
Personally, I prefer the space gaps as it helps with visualization. When patterns/samples change it is easy to visually identify which one is which. Probably my workflow is locked in at this stage but my eyes don’t identify with the Ableton screenshot.
but we do NOT review the forums for ideas and features, and if you do not move this to tracker.ardour.org then we will simply forget about it/ignore it.