Funny you should bring that up, it's the main reason I wrote this post. I've been thinking about the portal issue and how much it will change the dynamics of the game once resolved. I don't think there is going to be a time overhaul anytime soon, along with a many other things such as disabling traps in adventurer mode, etc. My main thought was starting out on a quest given to you by a lord or something to go colonize a place and so on and so forth, you get there, then there could be a "Start a Fortress" option, in the retire screen. Adding on to that, maybe have a slightly modified embark screen with whomever and whatever you have with you.
It would be neat if it was a seamlessly integrated part of the game, being, no switch whatsoever, but I can see something like this kind of working for now. e.g. when you broke into candyland the fun was simply a statement and your fortress was to be explored via adventurer, but now clowns come out to play, and I think it was well integrated. That being said, there weren't the same issues, but, I was thinking more terms of how having this kind of system set up could have an impact in the late gameplay. Such as, starting a character to make their family to start their own nation eventually and bring glory over generations of expansion.
Plus the journey for the embark spot could be fun!