Don't fixate on just punishment for killing bikers. If you want a piece of legislation to be well received, look at a well rounded package in terms of education, enforcement, AND punishment.
Education: require driver's education courses and licensing tests to have a section that focuses on awareness of motorcyclists (and scooters, bikes, trail horses, etc).
Education isn't just for the cagers. Being safe and smart keeps us alive. Look for DOT incentives to get riders to take MSF courses. For instance, make it more enticing (easier/cheaper) to take the MSF and get educated and licensed than to just get temps and muddle your way into a crash.
Enforcement: Educate LEO on the additional hazards that motorcyclists face (credits for MSF training would be great). Have law enforcement issue citations to people that cause hazards for motorcyclists whether there was an accident or not, because the first accident can be fatal.
Punishment: Killing anyone should certainly have a pretty hefty punishment. Mandatory jail is a tough one to get people to vote for (and an issue for you to get elected on) and judges don't like laws that don't give them the ability to weigh the contributing factors (and we know no biker has ever ridden drunk, right?).
But don't just focus on dead bikers. In WI we have a law that any accident involving a motorcycle requires the driver that injured the motorcyclist to take additional driver's education classes. And that can be backed up by suspending their license.
Here's a brief write up of the laws we got a couple years ago here:
http://www.amadirectlink.com/news/2006/WIlaw.aspGood luck, and thanks for trying to keep bikers alive.