@Azzanation I did this research recently, maybe it will be better suited here 
343 Leadership
CVP, Head of 343 Industries
- Old: Bonnie Ross (2007-2022)
- New: Pierre Hintze (2022-Current)
Pierre is known as the guy who fixed the MCC but it of course was a team effort. He joined 343i in 2018 as Head of Publishing in their secondary team working with external partners, the primary team being the mainline titles, Pierre was tasked with leading the Master Chief Collection repair efforts which he did so brilliantly. The MCC before 2018 was an absolute mess, since Pierre took over it was updated massively and added more content than was ever promised.
Pierre's expertise are mostly focused in production and producer roles as well so his experience is managing teams.
Franchise Development Director
- Old: Frank O'Connor (2008-2023)
- New: Corrine Robinson (2023-Current)
Frankie was essentially the 2nd in charge of 343i behind Bonnie Ross.
Head of Transmedia and Entertainment
- Old: Kiki Wolfkill (2015-2023)
- New: ????
I'm unsure who replaced her or if she simply moved outside of 343i, I have previously speculated that maybe the whole Transmedia team inside of 343i was moved outside of 343i to be less of a distraction for Pierre.
Kiki was essentially the 3rd pillar of 343i back in the day, alongside Bonnie and Frankie.
General Manager (New Role)
- New: Bryan Koski (2022-Current)
I believe Bonnie Ross was Studio Head, CVP, General Manager, etc. Bunch of roles mixed into one, Pierre upon taking over her role decided to split it up and spread it out, likely because it was ridiculous for one person to have all those roles and responsibilities.
Chief Operating Officer (New Role)
- New: Elizabeth Van Wyck (2022-Current)
This was another role in which Pierre decided to create upon Bonnie's departure instead of being in charge of everything.
Studio Design Director
- Old: ????
- New: Max Szlagor (2023-Current)
I'm not sure if this is a new role or simply an old role slightly renamed, I'm not a developer, Lol. I see 343 had a Live Design Director, Multiplayer Design Director and Narrative Design Director but I can't find a Studio Design Director before Max in Halo 5 or Halo Infinite credits. Could it be Chris Lee's role but with a slight name change? (Studio Design Director/Studio Director?)
Anyway, Max also comes from Pierre's former team, he joined the MCC team in 2017-2018 as Design Director and also credited for positively changing the MCC from the state it was in alongside Pierre and others.
Studio Director/Head of FPS Development
- Old: Chris Lee (2016-2020)
- New: ????
I'm not sure who has replaced him, I would speculate either it's Max Szlagor's role or Pierre has absorbed this role.
Head of Design
- Old: Jerry Hook (Halo Infinite-2022)
- New: ????
See below.
Lead Game Designer
- Old: ????
- New: Dan Gniady (2024-Current)
Did Dan Gniady replace Jerry Hook? Lead Game Designer and Head of Design sound like the same thing to me.
Multiplayer Creative Director
- Old: Tom French (Halo Infinite-2022)
- New: ????
I can't find his replacement yet.
Lead Multiplayer Designer
- Old: Andrew Witts (Halo Infinite-2022)
- New:
I can't find his replacement yet.
Forge Lead
- Old: Tom French (Halo 5 Guardians)
- New: Michael Schorr (Halo Infinite-Current)
Head of Engineering
- Old: David Berger (2007-2022)
- New: ????
I can't find his replacement but I assume his departure was down to them switching to Unreal Engine.
Art Director
- Old: Nicolas Bouvier (2014-2022)
- New: Chris Matthews (2022-Current)
Cinematic Director
- Old: ????
- New: Josh Daniels (2024-Current)
Unsure who the previous Cinematic Director was.
Chief of Staff
- Rob Semsey (2017-2022)
- Melissa Boone (2022-Current)
Rob Semsey is still at 343i but he is now Director of Communications so he has replaced someone there.
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This isn't an extensive list because it obviously doesn't include the 100+ layoffs from the Campaign team, it's largely focused on the leadership roles, the Campaign team was gutted so they're going to have to be rebuilt and the leadership team has been almost completely revamped, others have departed here and there too which I haven't listed.
Comes across like Pierre and the MCC (2018+) team took over the main team and he has switched some roles up, streamlined a lot of processes and some roles in the two years he has been in charge and now after clearing up some of the mess, he is preparing to gear up for the full-scale ramp up. I'm going to remain optimistic and let him cook, he clearly cares for Halo and understands a lot about it based on previous interviews.
