Please add l2tp support
IPsec/l2tp is a quite common configuration in the Windows (and in the MacOSX) world.
It could be nice if l2tp support was added at some level to make it easy for the end-user to connect to such setup.
This is probably not needed when using static tunnels, so I guess this may be added to the network-manager module.
The following module0 as well as the nm-pptp module could maybe be used as inspiration.