I found a bunch of threads but I think they all add up to no, there is no direct way of importing historical managers. The closest thing to it would be the capability of exporting and importing team strategy settings as shown below - players use that to transfer them from team to team and game to game. It appears people edit historical managers manually and guess as to their strategy settings.
Here are the threads:
http://www.ootpdevelopments.com/boar...-managers.html
http://www.ootpdevelopments.com/boar...-strategy.html
http://www.ootpdevelopments.com/boar...l-mangers.html
http://www.ootpdevelopments.com/boar...-managers.html
Anybody else know better?