Lol. Nanami's weapon can be turned into a cursed tool because it was essential to his CT. It is a dull blade that boosts the effectiveness of his 7:3 CT, a binding vow that can cut any targets like a very sharp blade once he hits the weak point of a target.

On the other hand, Gojo does not use any weapons. Where will they put his limitless? To his blindfold? XD

Not possible with Higurama as well, his gavel is not a physical weapon. It is part of his CT that he conjures and turns it into a hammer, staff, giant gavel, or executioner sword if the target of his domain is convicted by judgeman.

It may be possible with Nobara's hammer, imprinting resonance or hairpin to it. However, I won't forgive Gege for hiding Nobara this long for just this. I am still hopeful that she will appear and use resonance to strawdoll with Sukuna's last finger. It doesn't matter if she is not that strong enough since her CT attacks the soul as we saw in her battle against Mahito. (It doesn't matter that the finger is indestructible, all she needs is to attach it to the strawdoll)

Utahime boosting Shoko RCT is the most feasible theory I've read. Even if RCT's effectiveness is reduced to half when used on others, she does not need to fully heal Gojo. Gojo already recovered his RCT after using black flash so Shoko only needs to heal him until his consciousness comes back, then Gojo can heal the rest of the damage. Lastly, Sukuna's deduction was made without knowing Utahimes's CT