I am new to openACS (have been 'experimenting' with it) and I customized the login page that I got from OpenACS 5.0.4 for a small HR application I am building, by customizing the script at /packages/acs-subsite/lib/login.tcl
I added a few ifs that used exists_and_not_null to check if certain parameters were sent to it and set up ad_form accordingly. After that I checked for the those parameters in the -on_submit of the ad_form. Hence I could get/set stuff from/to my app's realtions with out touching OpenACS data model. While doing an <include src=> in my app I would simply
set those parameters. The default login page still works like before and yes.. if the user choose to login via the default login page, and not my app's home page, then when the user visits my app's home page for the first time, he/she has to choose certain things before proceeding.
