Are you proposing a budget type system so it is more like a proper Fantasy F1 rather than a tipping comp?
I guess the system Giles ran was good. Each person has a mix of Team, Engine and x2 drivers. Has to keep under say a $40m budget and only allowed one change of each field over the year. Points are based on positions gained + final points position(like you have in the actual championship). It gets a bit complex though, don't know if you are willing to do it.
Otherwise you could maintain the exact same system as you have now but add a budget component. That way it will force players to be unable to pick button, vettel, webber, hamilton, alonso, massa every race.