Andreas,
Thank you very much for the thorough response. I was hoping that you would respond to this discussion as I have been aware of your involvement with Ecomize and the very successful implementation at London Hydro. I to deployed a custom logon app but it was mostly to modify the logon screen and make it compatible with HTML5 and CSS3. I still relied on the "j_security_check" functionality that is part of the standard delivery. If your company implemented a fully custom logon process, I would guess that you were able to accomplish this by replacing the SAPJ2EEAuthenticator class that is referenced in the NWA settings?
Good to know that the initial process occurs within the LogonAction class and then redirects from there utilizing the methods of the UMFactory.
Thanks again for the response. It helped clear up all the questions that remained for me in regard to UCES.
Time to start customizing UMCUI5 now haha.