I don't think Ben and Whidemore overlap because the history we seem with Whidemore... Penny specificlly. Doesn't mean that Charles wasn't the speaker for the island, which makes alot of sense now, but I don't think he was the one before Ben. Maybe he was the LAST one before ben and that's why Richard needed Ben. To be there leader, because we never saw Ben take the reigns of leadership from another speaker.