Add package customisation/power user features as an installation step

Considering the very minimal amounts of steps at installation it sometimes leaves users plenty of waiting time. Many of those users also know exactly which actions they will do and packages they will deploy at first launch. How about adding an optional "day 2" feature which would permit to install more packages than what is available?

My fantasy scenario: after partition+users+timezone were configured there is a synaptic window step allowing to click on more packages during base install is happening. After this original system install and right before reboot a 2nd round of apt installs would take place based on those extra packages and then final remove media+reboot happens.

xo