(SPOILERS) What if.... there was another way of Sealing Nyx?

Spoilers for those who have not finished Persona 3 yet

I know the main character uses himself to seal nyx

But what if... there was another way of Sealing Nyx? I always thought about this ever since the final battle

And it could make for a very good discussion topic or an idea if Persona 3 ever gets a remake

(Hopefully with a better tartarus...)

So if you have any other idea of Sealing Nyx what would it be?