Note however the following (copying from: http://pgina.org/faq.html):

"Do shared services and devices authenticate users via pGina? - No. pGina is intended as a replacement for the *interactive* login process. Access to network shared items like printers, drives/folders, etc on another machine - do not use the portion of the OS that pGina provides replacements for. That said, the 3.x architecture does allow for this kind of thing in the future, by moving much (arguably all) actual processing into a dedicated service, *any* part of the OS which can be augmented, could potentially validate credentials using the pGina framework. For things like shared services, this would require an LSA module. This is outside the scope of the pGina project, but we've tried to make it flexible enough that experimentation in this area could be done!"

So, it may not be suitable for your case where authentication (against LDAP) to shared network resources is needed.

Therefore, if you don't want SAMBA (I am interested to hear of any arguments against its use), there might be no other alternative than to set up Win/AD.

Nick