@Scott - I understand your opinion but when Unity themselves tell people to use object pooling
http://docs.unity3d.com/Documentation/M ... ement.html (near the bottom) then you have to expect that some customers will want to do it. In that document they mention using pooling for projectiles and that is one of my use cases, I'd also like to be able to use Chipmunk for some particle effects too.
There are also several 3rd party pooling libraries and PoolManager is currently number 1 in the scripting charts and the second most popular asset in the current "Madness" sale.
AFAIK all the pool managers work by having a pool manager object in the scene graph that instantiates prefabs and keeps inactive objects as children i.e. they are simply activating and deactivating game objects as you suggested. Chipmunk2D seems to work in this context but I haven't tested it extensively.
It is something I want to do so I'll plug away and see how I go. If anybody else is interested in getting Chipmunk2D to work with a pool manager please speak up.