How can a cPanel dedicated server be used in order to
offer adsense powered hosting, any method or idea how
you can preload adsense or other ads for all or specific
accounts inside the sites ?

Greetings,
Are you wanting the ads to display on cPanel or the customers websites? If you want to display ads on your customers sites, you should look at a program called iAds (http://www.ihostdev.com/iads.html). The only problem is you must be root on the server to use this application.