Which Daedric Prince Do You Think Will Have The Most Impact In TESVI?
Malacath: I think he has the highest chance of being significant, what with Orsinium being recently rebuilt and so near both Hammerfell and Highrock. However, I feel Malacath would better serve as the antagonist of his own DLC (a la Bloodmoon, Shivering Isles, Dragonborn) that focuses on Orsinium and the Orcs.
Peryite: While this may be due to my personel bias, as Peryite is my favorite Prince, I feel he could hox an interesting impact on the plot overall. While it'd be easy to just say "There's a plague and Peryite is behind it, you must stop him!", I think that if the rumors/leaks/ theories are true and the Dominion is going to try to destroy the Adamantine tower to unmake Mundus, it would be far more cool to have Peryite be a strange ally against them. This due to his domain in part being keeping the fundamental order of Oblivion intact, and the destruction of Mundus would definitely encroach upon that.
Namira: My theory behind Namira being significant would only work if High Rock were in the main story. With the civil war in Skyrim, High Rock has been cut off from direct access to the empire and imperial support. This has lead to famine and poverty on an unseen scale, all while the various kingdoms increase taxes to cope with the loss of trade, allowing the influence of Namira to grow at an unprecedented rate. I imagine this would lead to a storyline inspired by the Peasant's Revolt of 1381. Though this may be better saved for a DLC as with Malacath.