Either of debian-reference-{de,en} suffices
Alternative versions of ubuntu-packaging-guide are fine, too
Declare this as version 11
Downgrade blhc and dh-exec to Recommends

They're not available on Squeeze
Prefer mcabber over cabber

The latter is no more available in more recent distributions.
Downgrade sirc to Suggests

It's no more available in more recent distributions.
Prefer vim-nox and vim over vim-full

vim-full is solely available in Hardy.
Remove tla-tools, soon no more available at all
kiva-base suggests kiva-users