Take a look into the preinst script:
In theory, you could do something like:
And have the dependencies be apt... However, I don't think you can require an external PPA and have package dependencies from them, as the dependencies download first before preinst or anything else is run...
# Double check root...
if [[ $EUID -ne 0 ]]; then
echo "This script must be run as root" 1>&2
# Then add a repository the standard way.
# And now you could just install the packages here.
apt-get install <packages>
However, personally I would advise against this except for private use, as it is definitely not the best way to do things and is quite ugly.