There is the option to add a "legacy draft" in Franchise. The way it is implemented though is a bit strange. If you select it, then the first year as GM isn't all that different, but the first postseason becomes radically different as hundreds of legacy players are suddenly made available for drafting such that teams can radically change their rosters.
Moreover, certain legendary players such as Henry Aaron and Rickey Henderson, are able to suddenly expand their iconic career records such as RBI's, homers, and stolen bases and hits.