It would be handy if you could assign maps to a group. When I am not travelling I usually have the maps of Netherlands, Belgium, Luxembourg and all the adjacent regions of France and Germany downloaded on my iPhone/iPad. When I go on a long cycling trip I add countries/regions as needed. To free up memory I sometimes delete some of the ‘home’ maps while travelling. Coming home I want to download the ‘home’ maps again. Being able to assign maps to a group would make this process easier.
Also you could use it to check the area covered by the downloaded maps by Viewing the group. (A bit like viewing multiple tracks at the same time by assigning them to a group.) For instance when doing a trip from Amsterdam to Rome you could add all the tracks/pins/poi AND MAPS (= NL/BE/some German regions/Switzerland/some Italian regions) to the same group. I know there is the Maps download feature along routes and tracks but I find this is not really useful since the window is to narrow in my opinion (see my other feature request about this)
Another handy feature regarding offline maps could be to show the covered area of the downloaded maps while at a certain zoom level. You could even color code this for outdated maps (e.g.: green for maps that are up to date, blue for older maps). See attached screen shot of OsmAnd for an example.