"Reasonable" ways of bringing Sanguinius back?

[Spoilers for End and the Death]

I know there's been a bit of discussion about GW wanting to eventually bring back all the primarchs, which of course begs the question of how could they do that with those who are dead.

In my case, I think the death of a character in a universe like 40k should be permanent, since otherwise it diminishes its dramatic and narrative impact.

With that said, however, do you think there are other ways of making Sanguinius have a presence in the current 40k setting, without directly resurrecting him? I'm thinking maybe have his soul possess a Blood Angel for a limited period of time, or be tied to a specific place, etc?

I think it might be reasonable to do something like that for Ferrus Manus as well, since, IIRC, in The End and the Death it's shown that his spirit still exists.