This deck sounds ridiculous...ly cool!
About the walkers, there's only bolas that's uncastable, right?
Have you given a shot at this? I'm pretty tempted to do so, as teferi is the only expensive card I don't have to play at mtgo (and which I'm still not really sold at for vintage). Spellseeker sounds a pretty cool new toy to this, being a tutor for broken stuff that can flashback therapy.
Also, I get the possibility for broken stuff turn 1 with moxen, but I think you have lots of 4cmc+ things that you'd probably only be able to cast turn 2+, I think it'd be good also playing sol ring.
One thing I've noticed is that you have 2 tutors and no demonic. I think that 1 extra mana is worth the investment to not lose card advantage. I may be wrong, given that the extra mana may imply in 1 more turn without the payoff walkers, but this deck sounds good for the long game too (which would make the card disadvantage a real drawback).
And with that many expensive spells and broken stuff your opponents will have I'd give a shot at mana drain (md probably 1 at least), and flusterstorm (sb).