Sounds like you might need to go a code route. Personally, I would use multiple spheres, that are connected with Spring Joints.
Then use Physics.IgnoreCollision to prevent them from messing with each other.
Then I'd connect the oobleck spheres with half hour glass shapes between each other, that resize and/or dissapear based on the size/distance of the ooblecks.
finally, I'd either work on writing the code for this, or purchasing an asset that can slice up models. I.e. oobleck through a fan. Though your still going to have work remerging/melting the oobleck in other ways.
*UPDATE*, I found this: I imagine you may be able to bend the code to get more of what you need, or use it as a base to rewrite your own.
Check out this: http://wiki.unity3d.com/index.php?title=MetaBalls (source shown)