Slaves should NOT be portrayed in the game in detail. It is just too insulting to many groups. However, at the trade nodes, if other commodities are portrayed, then slaves could simply be another commodity along with INDENTURED servants. In the same way the Hearts of Iron series should never portray the Holocaust against the Jews in detail.
See that's where I disagree with you. I shouldn't announce this publicly, but just to make it clear my father is Jewish and I received a bar-mitzvah, so I'm saying this as someone who strongly feels for the Jewish people. The holocaust used so many resources in so many places that could have been used towards the war effort. Not portraying it skews the strategic decisions made to keep the holocaust running at full speed at the expense of the front line soldiers and their ability to be resupplied. HOI should surely have modeled it in some way. These events happened, it's not for us to judge them as not happening because they offend us. Not portraying something of such magnitude invites the criticism that its exclusion from the scenario A)absolves the Nazi's of their historic prejudice and potentially allows you to play the Axis as pure good-guys in your mind, and B)actually is insulting to those involved. No Jew wants to play through the holocaust, but we're talking about text pop-ups that allow the game to better reflect the situations involved without moral judgement involved. To simply pretend it didn't happen is playing it safe at the expense of perceived reality. In many ways you are saying that a company should deny the holocaust since it is a controversial subject. Education is the solution, not exclusion of events.