Yes actually before I made this I made an average of a bunch of play-throughs I found for Remake Part 1 to see roughly how long each chapter was. I got something like this:
Chapter 1 – The Destruction of Mako Reactor 1 1H
Chapter 2 – Fateful Encounters. 1H
Chapter 3 – Home Sweet Slum. 2.5H
Chapter 4 – Mad Dash. 1.5H
Chapter 5 – Dogged Pursuit. 1H
Chapter 6 – Light the Way. 1.25H
Chapter 7 – A Trap is Sprung. 1.5H
Chapter 8 – Budding Bodyguard. 3H
Chapter 9 – The Town That Never Sleeps. 4H
Chapter 10 – Rough Waters. 1H
Chapter 11 – Haunted. 1.5H
Chapter 12 – Fight for Survival. 1.25H
Chapter 13 – A Broken World. 1.5H
Chapter 14 – In Search of Hope. 3.5H
Chapter 15 – The Day Midgar Stood Still. 1H
Chapter 16 – The Belly of the Beast. 2.75H
Chapter 17 – Deliverance from Chaos. 3.25H
Chapter 18 – Destiny’s Crossroads. 1.5H
Total 34 hours
Most chapter range from 1-4 hours roughly. Most are between 1-2 hours whole some of the long ones that include a lot of side quests and mini-games go 3-4 hours. The Wall market Chapter took the most amount of time and that's why I made sure I put 4 hours or so for the Gold Saucer Chapter.
If I was to split Rebirth by chapters I might do that following:
Note: My chapter map is skipping For Condor for now. I've considered that they might find a new way to to get to the Gold Saucer from Costa De Sol since going through the Mount Corel Trek might take up even for time. They could potential save Mount Corel for when we are playing as Cid going for the Huge Materia in Part 3. I'm not sure though they could still have Mt. Corel. I'm also not doing Wutai for now.
Actually it's basically how I laid it out anyway. I think they will just have more chapters than part 1 since it's a longer game. I don't think it has to line up with 18 chapters.
Chapter 1 1H Nibelheim Flashback
-Tutorial, First Boss fight Green Dragon
Chapter 2 2H Kalm and Surrounding area
-Small town, introduction to Red XIII combat, some sidequest and travel/exploration
Chapter 3 1.5H Chocobo Farm and Zolum
-introduction to riding chocbo's perhaps, maybe we'll have more chocobo riding than the OG game?
-Boss Fight Zolum
Chapter 4 1H Mythril Mines
-Small dungeon
-Boss Fight Turks, introduction to Elena
Chapter 5 1H Meeting Yuffie in forest
-exploration, see Fort Condor in Distance
-Either Yuffie as a Boss Fight or she joins some other way
-Possibly involve playing Fort Condor mini-game
Chapter 6 2.25H Junon Lower town
-Larger Town, Sidequests, Bottomswell Boss Fight
Chapter 7 2.25H Upper Junon Barracks
-Minigames Parade
-Possibly meet Roche here
Chapter 8 1H Cruise Ship
-possibly continue with Roche
-Might not fight Jenova here, might be too early in game
-It may be why the fight got moved to the Shinra HQ in Part 1
Chapter 9 1.5H Costa del Sol
-Small Town Chapter, Sidequest + minigames
-Johnny meets Roche? (lol)
Chapter 10 4H Gold Saucer (includes Corel+Prison)
-This is the big Wall Market Chapter, probably extravagant
-Meet Cait Sith
-Possible Boss Fight that wasn't in OG, in colesseum? move Tankceratops here?
-Will probably have Dyne as a solo Boss for Barret just like OG
-I assume chocobo racing and getting the Buggy at end
Chapter 11 2.5H Cosmo Canyon Village (includes Buggy travel)
-traversal with the Buggy hopefully with a large area to explore
-Cosmo Canyon medium town chapter
-sidequest and lore dump/story sutff
Chapter 12 1.5H Cave of the Gi
-medium to large dungeon Chapter
-Boss Fight Gi Nattak
Chapter 13 1.5H Gongaga (Includes travel)
-interesting story stuff, does Cloud remember more than he did before?
-Will we switch to Zack at some point? maybe around here? not sure
-Boss Fight with Reno and Rude, Tankceratops Boss Fight if it wasn't Gold Saucer
Chapter 14 1.25H Nibelheim town (includes travel)
-small town mystery, a bit of story stuff
Chapter 15 1.5H Mansion and Vincent
-Dungeon chapter
-get Vincent
Lost number Boss Fight
Yin and Yang Boss Fight
Chapter 16 2H Mt. Nibel
-Large Dungeon Chapter/exploration
-learn Vincent combat
-interesting story stuff at Mako Reactor
-Green Dragon Boss Fight (again)
-Materia Keeper Boss Fight
Chapter 17 1.5H Rocket Town
-medium Town Chapter/sidequest
-get Cid! Story stuff
-Palmer Boss Fight (maybe he was a weapon or vehicle)
Chapter 18 3H Return to Gold Saucer (includes travel)
-It's possible we don't get to paddle around in the water
It might be done in a way where we go straight to Gold Saucer but who knows
-there could be some element of travel/exploration/finishing side-quests
very similar to Chapter 14 in Remake Part 1 here
-Date with one of the party members (hopefully Red XIII) lol
-possibly changes the way the keystone story stuff plays out
Possible Boss Fight here involving Dio's Colosseum
Chapter 19 3H Temple of the Ancients
-Large Dungeon Chapter
-Lore/story stuff here involving the ancients and the Planets history
-Boss Fight Red Dragon
-Boss Fight Demon Wall thing
Chapter 20 2.75H Sleeping Forest and City of the Ancients
-Large Dungeon/exploration Chapter
-I won't speculate too hard on what may or may not happen here
Chapter 21 1.5H Icicle Inn
-Small Town Chapter
-Elena Boss fight
-Snowboard section might be done similar to the Motorcycle chapter in Remake Part 1
Chapter 22 1.5H Snow Fields
-Dungeon chapter
-meeting Holzoff
Chapter 22 2H Gaea's’ Cliff
-Large Dungeon/exploration chapter
-Boss Fight Schizo
Chapter 23 2H Whirlwind Maze
-Finale
Open to speculation how it plays out