Blood Games 4 uses the StarCluster 4 system, which is robust and flexible enough to accommodate the differences in genre without using exceptions. I have made Player's Option characters, who are different because of what they are, as species, while Path characters, who are different because of what they know, as Template Trees.
OHMAS will become a Blood Games Toolbox for Renaissance play, probably called Blood Games 4 - Renaissance, and Outremer will become a setting for Blood Games 4 with that Toolbox. This will make Blood Games development easier, and new stuff will follow that pattern.