She already soft counters what we have now.

Uchiha/dodge. Kushina plays the lowest HP game quite well against these dodge heavy characters.

She can completely nullify the popular Kurama/Roshi combo and even soft counter Wind Main's resets with Itachi Susano.

Comparing a barrier anti-battery ninja to a ninja with a kit that specializes against immunity, isn't necessarily the best *ogy

Roshi's no longer a dominant position 1,

He's doormat for his chase and great slot potential. Additionally, alot of NInjutsu focused ninjas are coming out that'll make him not as much of a safe front.

Outside of that, there's really not much to say.

Kyuubi Naruto is still one of the overall hardest hitting ninjas, Kurama will be god for a lot of reasons for quite awhile.

Kushina doesn't nullify him, Roshi however....

If I were to guess, Probably S tier, or S+ at best since he feels to easy to counter and lack of heft to his mystery leads him not feeling god like without huge stacking, and thus makes him not much of a star member in 1 v 1 setups. On the other hand his nature as a universal buffer and universal element based buff receiver mean that the amount of teams he can slot into is huge, which is why i wouldn't rate him to low. He also can have the distinction of being being one of the best partner ninja for blitz pairs is db, with extra points do to having synergy with other edo lineups.

Dunno if somebody already mentioned it, but I don't really get why 6 paths naruto is ranked the same as kurama. I can see Kushina being ranked higher than 6p, especially with her breakthroughs. But 6p naruto is superior in almost all ways to kurama naruto (and note, i'm talking about the sage of six paths naruto, not 6 tails kyuubi naruto).

To compare;

6p naruto's mystery can hit multiple teams at once while interrupting. Kurama only hits one team and doesn't interrupt (other than the one selected ninja he chases).

6p naruto's chase removes buffs and shields + immobilizes. Kurama's chase, though undodgeable, only deals immobile.

6p naruto heals based on nin dmg dealt, if he mysteried. Kurama doesn't heal himself at all.

6p naruto's standard hits 2+ ninjas and deals frankly massive dmg while usually critting. Kurama only hits one ninja (+ repulse dmg).

Considering neither ninja scale permanently, 6p naruto with his heals and bigger dmg output + buff/shield removal + interrupt is definitely superior to Kurama. So putting them both at 'S+' rank in the General and 1v1/Space Time rank seems kinda off to me.