What about the Victorian era picking up where Blackadders Christmas carol left off.
Have blackadder as a factory owner attempting to make his fortune (but never quite succeeding).
Hugh Laurie could be the kind hearted but very dim-witted upper class type who's father invested in Blackadders business and left the shares to George in his will meaning that much to his irritation Blackadder has to be nice to him and is occasionally humiliated by having to share half of the profits with him. This would however also allow for Blackadder to use him as a cash cow for various things.
Bring back Steven fry as a slightly meaner version of Melchet who could either be some sort of government minister or principle shareholder or possibly even a dim-witted but mean spirited Lord Cardigan like senior army officer. Essentially a slightly crueler version of his Blackadder goes forth counterpart but equally oblivious to the suffering and unnecessary loss of life he causes to the men he commands.
Whatever his role he must be of much higher station in life than Blackadder.
Bring back Darling to be Melchet's aide and blackadders bitter rival.
Baldrick would maintain his role Blackadders dogsbody and maintain all of his traits and cunning plans.
Have a succession of poor and or crippled orphans comprising the workforce to whoms suffering (and extraordinarily high mortality rate) the main characters are completely oblivious too with the exception of Blackadder and Darling who are merely indifferent with occasional sadistic moments.
At some point have an episode with Bob in which Blackadder has an affair with her which is strongly hinted to result in offspring that becomes Captain Blackadder of the third series.
Episodes could deal with things such as the industrial revolution, Jack the ripper (accidentally killed by Baldrick), annoying do gooders, the various screw ups of the crimean war, Blackadders disgust and hatred for the poor of London that comprise his workforce, ect.
Finally bring back Brian Blessed as Queen Victoria because why not?