I just talked to a cups developer and I was told that for just printing directly to a printer there is no need at all to install cups. All that is needed is the printer .ppd driver, ghostscript and tools to create postscript files from different files like e.g. a2ps or convert. At least for network enabled printers that should work.

Printing then basically works like this:

- have some file to print, e.g. hello_world.txt
- create a postscript file from it (a2ps hello_world.txt > hello_world.ps)
- pipe the postcript file through ghostscript using the right options (gs -option1 -option2 ...)
- send the result directly to the printer using netcat

That way cups can be completely avoided. To create the correct options for ghostscript one can simply
- setup a queue for the required printer driver on a normal cups server
- set the cups logging to debug
- send a print job
- search in the cups log file for the ghostscript command and the used options.
- one can repeat this for several driver settings like photos or text files and then have some script that converts depending on the input format to different qualities.

I have not yet tested all that but plan to do asap.

Additionally i was told that many printers are able to also directly process some file types like e.g. jpeg or text. One can try to simply send the files to the printer using netcat, usually port 9100 should be working (but that was just from experience).

If one has a print server running (that has the drivers configured), then just installing cups-client might of course be the cleaner solution.