I see, NB interface doesn’t allow a redirect to be set as homepage in the first place.

The option isn’t there; it is impossible to begin with.

A redirect is not a page. It is a link that goes to another page. You cannot set it as a home page. It is not a page – it is only a reference.

Yes, and that doesn’t get me what I need.

Does using a redirect as the front page cause any problem beyond the logging in issue? Reading between the lines I’m getting the sense that it does…

If you don’t want the site to be public, just go to Pages > Settings and select that only interns or above can see the site. There will then be a login form and nothing else on the site. Using a redirect page type will just make it hard for the people who do need to use the site to log in.

Additionally, the Settings page now also has a check box for hiding a site from search engines.

We want to use NB as a CRM, without diverting traffic from the main site. So we don’t want to just use links because we don’t want to have the NB site be public facing. We want to ensure that people visiting the NB site are redirected to the main site.

Will using a redirect as the front page of a nation cause any complications?

You want the home page to be a non-nationbuilder page? Just use links between the two sites, no need to make a redirect – http://nationbuilder.com/coordinating_nationbuilder_with_other_cms