Is there a preferred way to create base images for Debian-based customized installations? We are currently going with multistrap but although it's better than hand-crafted chroot stuff, it still has a lot of edges and corners. Is there a more reliable and less error-prone way to produce a root filesystem of a Debian installation with some additional .debs installed?

(I don't want to send out a Debian installer with a preseed file though.)

Addendum 1: To clarify things a bit: We are delivering some kind of software appliance to our customers. That is, a debian operating system, with some additional software packages -- both our own and third-party ones -- and some configuration changes. To ease the installation process, we have an installer that does nothing more than partitioning, copying files to the partitions and setting up grub. So it's basically an image-based installer. So we are basically running the debian installation ourselves and just distribute the already installed operating system.

The question is about the installation part. I want to have that as easy and robust as possible, and of course, it should be an automated process.