Just as a small correction, I haven't been working on a persistent world mod. I have only been working on expanding the customisation process and the linked mod is simply an 'enabler' using the games current constraints to simply allow 3 and 4 to control a henchman. I am trying to deal with an 'extended' which allows multiple customisation of 4 source-hunters at the same time.
Thread here: http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=520328

Whilst multiple instances of turned combat might be already in (I would need to boot up the game to check..), there is no current macro-area at the same time. As for persistant world, it would require the ability to host a server. This is something I don't believe is currently supported or implemented.