Jokes aside, getting anything to S-Class this quickly is... unbelievable, in the bad way. It damages suspension of disbelief.
To be fair we've been doing pretty much everything we can to boost our speed, both OoC and IC
Consider that Hisana has been training into the ground for years, using techniques that wouldn't normally be available to the standard academy student-then Genin. Combine that with extremely early awakening of Sharingan to make learning much, much easier and then sealwork to give a large backlog of energy that she can tap into and a seal which allows her to basically, for a few milliseconds at a time, use Shunshin to it's utmost ability. I can see us having insane bursts of A-S class speed followed by short periods of recovery.
And honestly, out of the 4 "common" stats most things use; Strength, Stamina, Speed, and Intelligence. The two we'd have the easiest time raising in the Naruto-verse are Speed and Intelligence. The first by abusing relatively easy abilities and seal work, the latter by access to foreknowledge and the ability to hyper focus on abilities we know will give us the most returns.
Strength requires either Sakura levels of chakra control, or Lee levels of perseverance and Stamina has diminishing returns and really doesn't play much part in anything unless you're pitifully undeveloped or have so much chakra you can power pretty much any jutsu with it. Hisana has gotten around that a bit with her chakra seal but it's a trump card to be used sparingly and has limited reserves that she has to refil. Not the "Eats some Ramen and a good night's sleep" dynamo that Naruto is.
Though, saying all that. If we could ever figure out a seal to place on our hands to spoof perfect chakra control to slap dash together a knock off of super strength jutsu, we'd be pretty well rounded and a serious A rank threat that really only lacks experience.
Edit: because we're sorta already doing that with the shunshin seal. Just a flash of perfectly controlled chakra on impact would be fairly impressive, or a seal that regulates chakra through the system at a measured and perfectly controlled rate
Edit dos: that can be adjusted up or down or outright disabled when we need to
of course
