What do you think about installing (could be optional) DRV files instead of the PPD files ?
The only drawback I can think of is that as it works now when using DISABLE_JBIG=1 the PPDs for printers that need JBIG1 support are not installed. This is not possible with DRVs as we can't rip out the JBIG1 printers from DRVs.
On the other side as JBIG1 will be free of known patents in all countries from 2012-04-04 onwards (http://www.cl.cam.ac.uk/~mgk25/jbigkit/patents/), the DISABLE_JBIG option won't be much useful anyway.
I'm attaching patch that enables to assemble and install only DRV files.
There's new DRV_ONLY option that enables this behavior (it's disabled by default)
and CUPSDRV variable that specifies where to install these DRVs (default is `cups-config --datadir`/drv).
'make drv' in ppd directory assembles *.drv from *.drv.in (assuming that you rename the *.drv files in repository to *.drv.in because they are actually only a templates).
Passing 'DRV_ONLY=1' to 'make install' then installs only these DRVs instead of PPDs.
(the initial idea was Tim Waugh's)