Well, people are going to freak out a bit with those turns close to the finish. Will it slow the speeds? Yes. The problem is how everyone in the 5s, 4s, and 3s thinks their Cavendish and deserve a good run at the sprint. You'll have people sneaking up on the inside where there isn't room, over-react to something, and they'll take some people out. The crash speeds will be slow though (<25mph).
Whenever we run the Driveway counterclockwise through the chicane, someone crashes in almost every race of the night.
(finish is on the bottom-left, the straightaway, about 3/4 of the way to the next turn)
http://drivewayseries.com/Course/Cou...4/Default.aspx
Still, if you have a non-technical course, then people will crash because the pace will slow, the pack will get wide, and things get dangerous. Not much you can do about it course-wise. Just keep hay bales up for the corners, posts, and hydrants.
I really do think primes will quell the crashing. If someone lights it up every two laps, nobody will be that fresh at the end. Maybe you can have a most aggressive award to encourage attacks (anyone in a break gets a point at the start/finish, and the guy with the most points wins, or best placing if it's a tie).
Whenever I have sprinters to protect, I just ride hard tempo up front any time the pace seems to be lagging. I'll attack mildly before the corners or right at the tops of hills to cause a massive accordion effect and keep people thinking about oxygen rather than stupid moves. Hard riding is so much safer.