I would love to see this feature added; or some way to "carry over" townies between different towns - quite commonly I start a map and play for like 2 days (game days) before realising I won't enjoy the map (not enough resources, too much work to get building space etc.) and just quit and start another town. I'd love to see an "abandon town" option which allows you to delete your map but keep the townies.
This works really well with narrative gamers, as it lets them/us (trying to be objective, but I'm definitely a narrative gamer myself) create a story not only in one map but over the course of the journey of a group of townies. Basically, what I'm suggesting is that the game move form being map-based with the townies on the periphery (basically just tools to create the map you want) to townie-based with the map on the periphery (just a playing field to set out the story of the townies). This would be a kind of second game mode - the current one could (and should) remain, but there would be an option to do things differently and refresh your experience. Basically you form a dream-team (with an option to randomise those starting townies if you wish) and focus on getting them installed in a town; if the first map you come to isn't suitable then you move on to the next one.
This would essentially mean a separate save folder for populations; basically each group of townies gets a whole file to themselves instead of being part of the meta-data of the map save (or however they do it now). That's a lot of infrastructure, so there would have to be an option to go with the "regular" setup for those who aren't so interested in the micro-story of the townies. However, if this were added then the immersion and entertainment potential for narrative gamers would be nearly limitless. Many Towns players (probably most) are already narrative gamers - you almost have to be to enjoy sandbox games where you are making up the story as you go along - so this would be a real boon to the fan base I'm sure.
Of course, this wouldn't be added anytime soon (or even in the forseeable future - it's more of a vague dream than a tangible goal), bt I would greatly appreciate it if the community and the Devs considered the idea

What's that you're eating? A nice, juicy apple? You weren't supposed to eat that you fool, you were supposed to make it into a pie! - last words recorded words of Francis D'Avre before he went looking for snowcherries, but found a hungry Yeti instead.