Hi Anil,
I do not see conflict between using SPS Federation Gateway as regular agent, but per documentation, there are limitations:
"Limitations of the CA SiteMinder® SPS Federation Gateway
Note the following limitations when using the CA SiteMinder® SPS federation gateway:
--The prefilters and postfilters (both built-in and custom-configured) do not execute when federation resources are being requested. For non-federated requests that are fired for the default context, these filters execute as usual.
--Proxy rules do not execute when federated resources are being requested. For non-federated requests that are fired for the default context, these rules execute as usual.
"
This indicates SPS as Federation Gateway does handle non-federated requests.
You may have to introduce configuration change in proxyrules.xml to make that happen.
By default, I think the login page is at ~/proxy-engine/examples/forms/login.fcc, if you want to change the look and feel, no problem. However if you change the default location, there are other setting needs to be changed as well, such as document_root defined under server.conf.
There is a section in SPS "Modify the Default Location of the SiteMinder Forms", a bit old, but give you an idea what may required when you do that. "Note: If you customize the location of the forms folder, ensure that you update the httpd.conf file with the location of the forms images. "
Depending on how much customization you would get into, CA service can always be an option if you are stuck.
Hope this helps.
Hongxu