I can’t answer that for you because of so many variables. You say 2-years on a 400cc. Is that daily 100+ miles or weekends only? Is that your commuter or weekend toy? Is that during rush hour or country roads? How many miles in 2-years? Year round or a snow climate six months of the year?Could you please let me know what exactly I have to learn after riding 400cc and before a Busa? When I say I'm gonna set a limiter and stay in mode C, I mean I don't die because of a 5-degree mistake on my right wrist. I respect Busa, and I also respect my Ninja 400; I can kill myself easily with both of them. But how many steps are there between them? Is it really necessary to get a 650cc, then a 1000cc, then spend years on them before getting on a Busa?
I’ve ridden motorcycles since I was 3-years old and crashed many times on dirt bikes. First streetbike at 11 and road it for years before I bought a liter bike at 18. Everyone is different and all experiences are different.
Be safe and call your insurance company for a quote before you do anything else.