Kobayashi would probably be a great driver for the car; he's aggressive, and with a high-downforce design and good rear suspension (something they'd worked on especially hard for 09) he could have seen quite a lot of success.
For a second driver, maybe Heidfield? Someone with experience from a race-winning team (or at least very competitive, like BMW in 08).
Update, again.
More small changes, and it's just about done.