Combine org nodes in separate files into a single tree recursively

Question

I want to compose "recipes," consisting of "subroutines" defined as org nodes in separate files, into a single tree.

I can't get the behavior I want because (it seems) the org exporter handles #+INCLUDEs iteratively.

The level of each node relative to the absolute root is not known a priori.

root.org:

* root
#+INCLUDE: sub.org :minlevel 2
#+INCLUDE: sub.org :minlevel 2

sub.org:

* sub
#+INCLUDE: subsub.org :minlevel 2
#+INCLUDE: subsub.org :minlevel 2

subsub.org:

* subsub

When I export to org (C-c C-e O O) I get:

* root
** sub
** subsub
** subsub
** sub
** subsub
** subsub

If I remove all :minlevel 2 I get:

* root
** sub
*** subsub
**** subsub
***** sub
****** subsub
******* subsub

What I want is:

* root
** sub
*** subsub
*** subsub
** sub
*** subsub
*** subsub

Is this possible?