One of the relatively recent commanders that's grown on me the most since it was first spoiled is Kytheon. He didn't appeal hugely to me at first, because no one thing he does is super powerful, but after considering him for longer I realized that his abilities have great synergy and work really well with equipment and board wipes. He actually has some interesting, subtle decisions to make, like when the ideal time to transform him is, and whether it's better to attack with an indestructible creature, let it attack au natural and untap it later to protect gideon if it survives, or just attack with gideon himself, or even goad someone else to attack. He's not an obvious flip-it-asap flip card, and he's not an obvious +1-until-ult walker. I think he's a really cool, subtle design, especially compared to the pretty banal nissa, jace, and chandra (lili gets a pass for being just crazy hard to build around).
Anyway, this is the deck I've finally put together. Happily, it also perfectly contrasts my Reyhan + Kraum deck which is the other deck I'm keeping together at the moment - it only shares 3 cards (2 of which are in basically every deck ever).
Kytheon is your swiss army knife, able to play a fast voltron as a 2/1 for 1 with a great ability, and then able to flip into a planeswalker later on to protect his team from board wipes, and still able to get into the red zone and finish people off with commander damage when the opening arises. The taunt ability is a bit more niche, and I don't love giving my opponents reasons to kill my stuff to avoid a suicide attack, but it could definitely be useful in the right situation to weed out utility dorks.
The creatures are frequently included to be good at surviving board wipes (man lands, token producers, etc) with a few, really powerful creatures that deserve to be protected by gideon's +1. Equipment-wise I mostly stuck with the cream of the crop. As far as board wipes, I think I'd like to go a bit higher, but this is probably a reasonable level for casual play.
Cards I excluded on purpose that would probably be pretty good: luminarch ascension, because it tends to make the game all about itself and totally overshadow the rest of the deck, and skullclamp, because I don't really have that many 1-toughness token producers and I don't think it's worth the hate I'd rightfully draw for the meager card advantage it's likely to actually generate.
Obviously mono-white is always a challenge, but I think this deck has the potential to be pretty strong between its early aggression, staying power, and heavy-handed removal suite. Nahiri was a ton of fun as a commander, and Kytheon follows closely in her footsteps I think.
First game went badly. People hated out jitte despite it being, imo, pretty mediocre in commander. Things were going pretty ok in the midgame between recurrable gearhulk and recurrable everything else with emeria + sun titan, but then keening stone of all cards came down with half my deck in my grave. For a few turns I danced around pretending to be helpful to keening stone player while trying to engineer a situation where he couldn't kill me with it so I could punch him for lethal infect, but it didn't work and he ultimately killed me with it. Wish I'd just forced the issue by cracking strip mine and forcing his hand, then killing him with infect before I lost, but oh well. Maybe mistveil plains, but that seems a little silly. Plus then I'd need to stick my fetches in it, eugh.
Second game was going well until the great aurora RNGed me out of the game with 5 lands off 20 cards. Still might have had a chance but it was late and the store kicked us out.
Third game was just last night. Was duking it out with niv 2.0 when Edric (UG) player went for sage of hours combo (tutor to top of deck with momir)...which kind of forced my hand against an otherwise pretty bad deck. O-stone was able to get me out of a tough spot with niv, setting back his mana a lot. I set up an infect kill against momir on the next turn to deny him pulling off sage of hours since I was out of removal, and then (despite being at 5 life thanks to quietus spike) was able to set up an infect kill against niv 2 turns later.
Rating: 2/5. The commander itself is a cool card but I never ended up flipping him, the deck doesn't have enough board wipes to reliably protect him I don't think. This deck did make me realize that I actually kind of hate voltron strategies, though, they're too slow and predictable, and (at least in mono-white) I didn't have enough answers to some of the crazier stuff that happened to really play control. The real nail in the coffin, though, is that nahiri just does the job so much better since she can recur your equipment, run more powerful board wipes and more of them, and can more reliably keep your equipment attached to things and getting value. And most importantly, she's way better with humility than Kytheon. Kytheon's biggest advantage is that he can do commander damage, and do it very early, but most decks can easily deal with him before he gets close to lethal commander, and that also tends to paint a bigger target on his back than just hitting with random tokens, and makes it harder to play control with him too. Sorry Kytheon, you're cool and all, but Nahiri is just a way more fun and way better commander for this deck.