Right about all except the for this -
"I believe, have been kept seperate from the main ROM in order to keep the Main ROM clean, small and responsive, while granting flexibility of choice to end users.
Thus, users may decide what to and what not to install"
It doesn't allow you the choice of what to install, it installs it automatically as a part of the rom (called "customisation"), you can't remove these programs and apps. They are generally carrier specific settings and apps that are generally refered to as "bloatware" and are generally hidden so they can't be removed.
ALL cooked roms are generally devoid of these settings and apps but chefs can add their own special blend of apps to a ROM they cook.
I prefer the big storage ROMs as they give me more flexibility to install or remove apps as I like and as most BS ROMs are UC compliant (user customisation) I can setup up what apps are installed on the device at startup and remove at will if an app becomes a nuisance. All UC apps are installed on the device memory, like an extended ROM, not the sd card.