We don't have any of these huge mountain maps (besides that one skirmish 3v3 map scythetwirler made in a19 committed in a21), because prior to sanderd17's patch the maximum height was 8 times lower.
About mapsizes, it's a big performance issue if we go beyond normal or large. Medium maps are good for 2-3 players if all of the terrain is accessible, but Normal mapsizes are usually golden middle.
I would like to see some more realistic mountains, but as wowgetoffyourcellphone correctly mentioned, it is important to keep it playable.
About this specific screenshot, I would make more area passable. Also notice place actor trees (trees that cant be gathered from) if they are inaccessible (otherwise units will try to reach it).
Also goats, right?