use parts of calibre

It is my first question in this forum. I have tried already to understand the parts of code of calibre. I am afraid without help I will not come further.

I have following idea. On a low resource system (OpenWrt - operating system) I would need just a small part of the calibre. Just one command called by Cronjob:

ebook-convert /opt/calibre/resources/recipes/foo.recipe bar.mobi

(You can than mail the output file using an external program.)

The advantage would be an access to the thousands of existing recipes (no need to reinvent the wheel). And of course the ebook-reader friendly output format.
The setup of the whole calibre would be difficult because of the lack of resources and unresolved dependencies.

How can I extract the right files from the source? Which files do I need?
How shall I put them on the right place?
Do I need a wrapper for the cli.py?
Which dependencies will have this part of calibre?
Is any further procedure needed (like install script from the calibre)?

My question goes in the direction of the http://manual.calibre-ebook.com/faq.html#id65 but afaik I know no binaries exist for the target platform.

Thanks in advance
Colinus