The drive modes have been around for a while in the gsxr600/1000 series. While it is an effective way to cut down the power & make the bike less volatile, don't forget that the busa weighs a lot more than the smaller displacement bikes.
That additional weight makes it all the more harder to control & learn on, especially for a newbie biker. Your skills would improve much more if you started off with a smaller bike & gradually worked your way up.
While it's not impossible to learn on a liter+ bike it's not recommended as you've already been advised by many bikers here. Just to give you an idea, i've been riding for a few years & even now sometimes when i crack the throttle wide open & hit the limiter i still get scared, the power delivery is so fast & ferocious. Experienced riders go down all the time, it's so easy to make a mistake it just takes a split-second. So a newbie being on such a machine is just asking for trouble.
Rest as a1ms said, it's your life & your money, seems like your mind is already made up. Ride safe whatever you do decide to get.