Stoneblade variants are popping up everywhere with the B&R announcement that occurred on 8/26/19. It seems like an early front-runner is strict UW, but plenty of Jeskai lists have popped up as well. This thread is to discuss Jeskai in particular until a clear best version is established.
For how I like to play magic, I want to maximize the powerful synergy of SFM into inevitability. I think the 2 equipments that will be auto-include are Batterskull and Sword of Fire and Ice. Sword of Feast and Famine is likely the next best sword, especially considering the recent uptick in Jund. The 3rd equipment I think will be very good is Basilisk Collar. It gives a mid-range deck an efficient way to grind out games and make combat miserable. Grim Lavamancer is a pretty cool combo with Collar, and I think some number of sideboarded Izzet Staticaster would be ok.
Using legacy Stoneblade as a template is a good start, but not strictly transferrable. We don't have Force of Will or Brainstorm so we will have to make do with other options. Serum Visions and Opt are the best cantrips, but I'm not sure which one to favor. I think at least 6 is warrented. I'm starting with a 4/2 split of Opt/Visions, just so I can keep up Bolt/Spell Snare/Opt in the early turns because t1 threats aren't a focus. Countermagic will likely be a mix of Spell Snare, Mana Leak, Spell Pierce, Remand, Logic Knot, and Cryptic Command. Cryptic on the upper end will be a little hard to support given the nature of wanting more gas instead of too much at the top end. I am thinking 20-22 lands, not the 24+ usually needed to support a full set of Cryptics.
Creatures are pretty easy to narrow down: Batterskull and Snapcaster Mage are auto include. From there I want a couple Grim Lavamancers and at least 1 Vendilion Clique. The closest True Name Nemesis variant I can think of is Geist of Saint Traft, which I think could be very good given the amount of cheap removal the deck can play. Restoration Angel could make it's way into the deck, but I'm not sure just yet.
Other cardsto consider: Lightning Helix, Electrolyze, Blessed Alliance, Fact or Fiction, Field of Ruin, Narset, Parter of Veils, Supreme Verdict, Anger of the Gods, Sunbaked Canyon. I will add to the list as other suggestions get mentioned.
To summarize: why play Jeskai Stoneblade? Stoneforge Mystic is a powerful threat with inherent card advantage, something that gives inevitability to a UWx mid-range strategy. It has the best unconditional one mana removal (Path to Exile), lets you play Lightning Bolt for reach, and lets you play Jace, the Mind Sculptor and Teferi, Time Raveler. If SFM is unbanned it will bring back Jeskai Mid-Range in a big way, and in my opinion it will supplant some amount of UW Control as a different option for playing 'good stuff' blue strategies in Modern.
Updated list 11/7
4x Stoneforge Mystic
3x Snapcaster Mage
3x Geist of Saint Traft
2x Brazen Borrower
1x Vendilion Clique
4x Lightning Bolt
4x Path to Exile
4x Lightning Helix
4x Serum Visions
4x Remand
2x Spell Snare
1x Force of Negation
1x Teferi, Time Raveler
1x Batterskull
1x Sword of Fire and Ice
4x Flooded Strand
3x Scalding Tarn
1x Arid Mesa
2x Hallowed Fountain
2x Steam Vents
1x Sacred Foundry
2x Spirebluff Canal
1x Seachrome Coast
2x Island
1x Mountain
1x Plains
1x Ghost Quarter
Sideboard
2x Alpine Moon
1x Celestial Purge
2x Search for Azcanta
2x Relic of Progenitus
2x Wear/Tear
1x Detention Sphere
1x Engineered Explosives
2x Stony Silence
1x jace the mind sculptor
1x Dispel
Update 9/20: This is a great list posted by 'xkeeperx ' that displays the Spell Queller/Teferi synergy. It's actually more prevalent than my 'niche' list above, so it's here for reference.
1 Batterskull
1 Sword of Feast and Famine
4 Snapcaster Mage
4 Spell Queller
4 Stoneforge Mystic
2 Vendilion Clique
1 Abrade
4 Lightning Bolt
3 Lightning Helix
2 Mana Leak
3 Opt
3 Path to Exile
1 Spell Snare
2 Spell Pierce
2 Celestial Colonnade
4 Flooded Strand
2 Hallowed Fountain
2 Island
1 Mountain
1 Plains
1 Sacred Foundry
4 Scalding Tarn
2 Spirebluff Canal
2 Steam Vents
1 Seachrome Coast
3 Teferi, Time Raveler
1 Sword of Fire and Ice
1 Relic of Progenitus
2 Geist of Saint Traft
2 Alpine Moon
1 Abrade
1 Ceremonious Rejection
3 Force of Negation
1 Hurkyl's Recall
1 Celestial Purge
1 Cryptic Command
1 Gideon, Ally of Zendikar