I'm not sure how this fits into the theory, but reading this thread I was reminded of the moment, back on the Shattered Plains at one of Elhokar's feasts, when Wit leans over to Dalinar and says "Adonalsium"
Dalinar of course has no idea what he is on about. But if Hoid sees Dalinar as a means to reassemble Adonalsium (or something more-or-less like Adonalsium, maybe with missing bits or with Intents mixed in different proportions)...could it be possible in the Cosmere for the re-forged Adonalsium to reach backwards in time to Dalinar, to plant seeds in the mind of its own future vessel, and that's what Hoid was checking for?
Or to go way off the reservation into Tinfoil Hat Land: what if Dalinar's visions are not about uniting the human kingdoms of Roshar, or even about uniting the humans and Singers, but instead saying the only real way to defeat Odium and end the Desolations is to re-unite the Shards? And/Or aren't even actually from Tanavast at all, but from Adonalsium II?
Maybe I've just got sleep deprivation and starting to babble