I think it would be really cool if you could take your
companions and start a fortress just about anywhere. I
notice in the arena mode it SEEMS to go back and forth
between adventure and fortress interfaces. Even if you had
to do a world save and then reload it in fortress mode like
you were continuing an old fort.
I feel it would add a cool new way to play the game,
especially if one of your companions was a dirty elf that
didn't like you cutting down those trees. If it would be
possible to start with the items in your collective inventories
(make sure you bring an axe and a pick with you) so much
the better.
If the process could also work in the other direction so
that we can assume control over a single dwarf in the
fortress, and play adventure mode as that creature that
would also be amazing especially if you can rejoin the
fort/claim leadership over the site. If it was not limited
to Dwarves then there would a lot of !!FUN!! possibilities:
Take command of your Militia Commander and lead
your comrades into battle!
Escape from slaughter: In the chaos of the Goblin/FGB attack
you might manage to escape with the clothes on your back,
items on the ground, maybe you can recruit people your dwarf
was friends with to take your lead and attempt to escape the
site alive.
Build your own sites with the tools that already exist in
fortress mode.
Play as that forgotten beast that you just found and take
out your old fort (or a challenge fort set up by a friend).
Sneak into a fortress as an animal man steal some items, run
away and find some friends to start your own
fortress!