Pattern for use of sub-pipelines to grab content at different stages?

[Craeg Strong]

Hello:

I want to assemble a web page the way a factory assembles a car. 
That is, I want to assemble a transmission, and set it aside (cache my 
header/footer)
I want to assemble a chassis, and set it aside (cache my user-specific 
menu bar)
Then I want to include the transmission, chassis, and frame into the 
final car (document).
I think I can do the above with cocoon using cacheable sub-pipelines and 
xinclude, is that right?

All the examples I have seen to date that use xinclude and aggregators 
don't seem to support caching intermediate products.

I asked the above question on the user list with no luck.  Any pointers 
are much appreciated!

Regards,

--Craeg