well could be,
Since his the so6p had his sharingan and kahashi could learn how to copy the move with his sharingan.
After all minato copyed the tailed beast bomb aswell, not like its his move either. And sage fought the juubi and was its host so he for sure would have seen a tailed beast bomb aswell.
But kishi most likely wont go down this road only because he wants to make minato's achievements unquie since he was kage. All kage's have their own unquie contributions.
I think you mean the So6P's had his Rinnegan, and I don't know if Kakashi had his Sharingan to copy the Rasengan as he created Chidori/Raikiri after failing to add his raiton element to the Rasengan. We know he had Raikiri before his Sharingan, so the timeline is off there, indicating he learned it with regular eyes. I believe Kakashi mentions this during Naruto's FRS training, as well we have the Kakashi Gaiden.
To the OP, it's implausible to me, but it's not provable/improvable either unless it appears in the manga. See the rest of my post below (based on the way Kishi has written about the So6P's).
Peace
not like minato would have known about the so6p let alone his skills.
Either way kishi would have to decided where to draw the line regarding so6p and where the generations after him achieved.
I agree, considering that many don't know much if anything about the So6P's to the extent that many don't even believe in him (considering him legend rather than fact) including some of the current Kage (see Madara revealing the Moon's eye plan at the Kage Summit), who were older than Minato.
There was no stone tablet that we know of aside from that left behind for the Uchiha that's progressively readable with the Sharingan->Rinnegan. As well, there were his treasures such as the Amber pot and those of the KinGin brothers.
Every time something of the So6P's is used, he's referenced, such as when Nagato used Chibaku Tensei.
Thus, it's inconsistent with the writing of the manga to have Minato not reference the So6P's and knowingly reproduce his jutsu. Leaving only the possibility of unknowingly doing so, which would cheapen Minato's legacy for no plot purpose. Thus my answer is no, it doesn't seem to fit Kishi's writing.
Peace