I'd really rather not touch the canon characters or events much, if at all. There's millions of years between the time the Ark took off and the Transformers within awakened on Earth going by the general G1 convention. Millions of years of possibility to explore as the Cybertronian race continued their conflict, their home planet now dead and ruined while basically all of their leaders and their greatest heroes dissapeared into nothingness. Lots of fun to be had around that time period, easy to create epic stories without ever coming close to messing up canon events in any way, shape or form.