Is this something that could be implemented once we have seraphis? I've been told it requires tx presigning from the xmr side.

I don't know. Someone like kayabanerve could take a look at the paper.

<xenu[m]> "Is this something that could..." <- I read it when I woke up and was going to say that on twitter but elizabethereum beat me

(Noot)

Seraphis will bring pre-signing