1, as far as I understand, is not relevant, but 2 is a big issue and 3 just makes it worse.
We're not too well-informed about the real practicality of non-standard sealing mediums, because Kagome tends to shut down those topics pretty quickly with stuff like 'it's insane don't do it unless you want to die'. We do know that Arikada managed to learn biosealing, largely by using other people as test subjects, and that (from what Kagome has told us) skin is not a stable medium and so if you put seals on yourself they're likely to fail and kill you.
My guess is that biosealing is perfectly viable if handled carefully, but you'd want to use any bioseals the same day or so to reduce the chance they fail on you.
Still, if we're looking at alternate seal mediums, I would like to again advocate printing press seals. They're incompatible with our current paradigm because the nuances of a brushstroke are meaningful in a way a stamp can't replicate, but if we can reinvent even just explosive seals in stamp-style we could collaborate with the Nara to make enough explosive seals to change the face of warfare again.
