Install openLDAP server on pfsense

As per openbsd doc (At some point anyway, pfsense was based on openbsd, as I recall - the pf packet filter is from Openbsd project) a bridge interface cannot have an IP, therefore it cannot be the captive portal:

http://www.openbsd.org/faq/faq6.html#Bridge

That said, perhaps you can try adding a third interface that does have an IP, and see if you can use PF rules to redirect traffic that crosses the bridge intended to someipaddr:80 to captive.portal.host:80 which is listening on that third leg of the pfsense system.

I don't think this is a bad idea, at least to try out for a day or two, but I'll give you a few reasons not to, since you asked.

1. One more point of failure
2. Misconfiguration can cause problems.
3. If you start adding firewall rules here, it can be harder to troubleshoot, especially for a junior sys admin. Is traffic being blocked here? Or at our normal firewall?
4. You still might want to add a 3rd NIC for out-of-band management; SSH, Syslog, etc.