Regarding the trap card Ajani Steadfast, I mainly plop him down for his emblem. His -2 is also nothing to scoff at when you have another walker that needs that extra loyalty to ultimate, and is also disgusting with rings of brighthearth. I have great experience with him and suggest you try him out one more time!

Jace, Cunning Castaway + Doubling Season gives you infinite jaces and infinite 2/2 illusions. His +1 can also be good if you're going the token route to win. Although admittedly, Jace, Cunnning Castaway is among the worst walkers ever printed.

Looking at Ixalan stuff, are you gonna replace Sorin Markov with Vraska, Relic Seeker? While Sorin does let you control your opponent with his ult, Vraska helps the token subtheme, she provides spot removal, and she sets the opponent's life to 1 instead of 10, which lets you overrun with your token theme even easier. This also provides a player kill with Ajani Vengeant, Ral Zarek, Samut, the Tested, or Ugin, the Spirit Dragon.

Also from Commander 2017, consider Ramos, Dragon Engine as a commander?

SithisAurelius

Vraska, Relic Seeker did make it in. I took out Garruk, Primal Hunter to open up the slot. Ramos, Dragon Engine also made it in.

Any new add-ons?

Wow awesome deck! You should try Genesis Wave It would be awesome to land many planeswalkers with one big spell.

Patiently waiting for an update with new includes.

One of the new transforming lands from rivals has been doing well for me. Azor's Gateway  ^Flip/Sanctum of the Sun is a bit of a long term investment, but it can go infinite for planeswalker activation with Kiora, Master of the Depths, The Chain Veil, and an untap creature like Fatestitcher (or Kiora's Follower if you are feeling flavorful)... should be noted that this would also work with any one land able to repeatedly produce 4 or more mana.

Also a great way to get extra milage out of Ajani, Mentor of Heroes ultimate... because having >100 isnt good enough on its own

Perhaps Abzan Charm over Ponder? It's a near another swords when you need it, card draw in a pinch, or a turn on Ramos ritual.

Oath of Teferi ... seems good

Dominaria is going to be insane for this deck list. Please continue updating, I will be back.

Finally, an actual use for my planeswalker collection! I am absolutely loving this deck, and I can't wait for an updated list that includes cards from Dominaria. Top notch stuff, mate! :D

Oath of Teferi time?

Are you going to be updating this deck anytime soon? I'm making a Superfriends deck (like everyone else right now) and would love to see an update list.