Alternatives to preseed installation?

[Christoph Mathys]

I'm interested to know about alternatives to preseed installations. As
endproduct, I require an image that I can restore with partclone. The
system is a customized installation of ubuntu-alternate. Our current
process to obtain such an image is as follows:
1. Create a preseed image based on ubuntu-alternate. All modification
need to be part of the preseed process.
2. Install this preseeded iso image inside kvm.
3. Use partclone to create the desired images from the kvm disk image.

I kind of think that it should be possible to eliminate the preseed
iso step. However, I fear that I just end up reimplementing a lot of
stuff that preseed already handles nicely. The annoying part in this
process is installing the iso image. This takes far too long if I need
to iteratively fix errors in the preseed file.

Any buzzwords or tools worth looking at?

Thanks!
Christoph