Pfsense connecting as IPsec client to a Cisco VPN concentrator?

[trivee]

My ISP has a VPN concentrator available to all of its customers, to be used with the Cisco VPN client on individual machines. I would like to use pfsense as a client for connecting to this VPN, so that the resulting tunnel could be shared by multiple NATted hosts on my home network.

I just started digging into this yesterday, and I already see the main problem. The VPN concentrator requires two stage authentication: mutual PSK + XAUTH. But pfsense only supports this mode as a server, not as a client - in ipsec.inc there's

'xauth_psk_server' => array( 'name' => 'Mutual PSK + Xauth', 'mobile' => true ),

And if I create a "mobile" Phase 1 definition for this, the resulting ipsec.conf has

rightauth2 = xauth

So, would I need to add a similar 'xauth_psk_client' option, and patch all the relevant code to generate ipsec.conf with "leftauth2 = xauth", to make this work?