What if we turn these stamp into some kind of NFTs that you can then stamp a hash into your messages and documents?
I'm sure Japan knows about e-signatures. The problem is that of "culture" perhaps? I'm not entirely convinced that this stamp-thing is a bad thing for Japanese culture, or that this is an issue that needs "fixing".
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But "if it does need fixing" (and again, I don't think I agree with that mindset...), e-signatures are readily available and easily done in Adobe-PDF readers, backed up by public/private key infrastructure given out by your company's smartcard system (or whatever).
Hanko culture, however, is harder to kill off. Part of that is things like more senior employees having larger hankos, needing to tilt your hanko signature to "bow" to your managers, etc. Japanese E-signature platforms generally have seals, and offer features to change the size of the seal, and to rotate it, to support the cultural aspects of hanko culture.