You might want to check out the modding forums then, specifically the DFusion and DFHack threads. You can use the DFusion follow function to "carry" as many retired adventurers as you want to an abandoned fortress, and when you reclaim, your adventurers should be present on the map as "Friendly" units. At this point, you can use Runesmith to turn him/her into a member of your civ (if the adventurer isn't the same race as your civ, you may need to use DFusion to get him to do jobs).
I've actually used Embark Anywhere to embark in a town where a previous adventurer had retired - unfortunately any inhabitants were hostile to my dwarves (apparently the human civ was at war with my civ), and so my starting seven was massacred. Still, I saw my elven adventurer listed as "Friendly" so if I had cheated using Runesmith to turn all the villagers friendly as well I could have gone on to build a fort with the adventurer as a member of the fortress.
In more exciting news, the new dfmode utility of DFHack allows you to switch over from fortress mode to adventurer mode, selecting one of your dwarves to become an adventurer. It's not perfect (you have to follow a complicated series of steps, crashes are common, and you cannot retire your new adventurer anywhere) but once it's cleaned up a bit it should open up lots of new possibilities.