So, investigating it further, looks like ONUW is feasible in some situations:
Doppelgangers, Sentinels, Revealers, and Curators are the only roles that cause significant headaches, and if used in the same game, it could be even more unwieldy. These first two roles would encompass a Night Phase A, where they would choose their targets immediately, and then all other actions would happen in Night Phase B. The last two roles technically suffer from having to occur simultaneously, and when combined with the Doppelganger... Well, whatever.
However, there is a bit of beauty to this, as we're less limited by the system, and using some rule changes would allow for an elimination of these issues as well as the usage of some more customized roles.
For those not in the know about One Night Ultimate Werewolf (and the Daybreak expansion), here's all the rules:
When the game starts, all roles in the game are revealed (equal to the number of players plus three). Randomly distribute the roles, and those unused are the Center Cards.
The game starts with all players using their actions of the role they start out as, and then play starts with players trying to figure out which role they have and their win condition.
The day ends and all players vote to lynch a player secretly. The player (or players) with the most votes is lynched (If all players receive one vote, no player is lynched.) If a Werewolf is lynched or no one is lynched and no Werewolves are in the Town, the Villagers win. If no Werewolf is lynched and at least one Werewolf is in the Town, the Werewolves win.
And here's the roles (as well as a close approximation to role priority):
Sentinel
Places a Sentinel Token on a player's role. That role cannot be looked at or swapped.
Doppelganger
Looks at a player's role and becomes a copy of it. They use that role's action.
Werewolves
All Werewolves learn each other's identities.
Alpha Wolf
SETUP: When an Alpha Wolf is in the game, add a Werewolf role from outside the game to the Center Cards (This card can be targeted the same as the other Center Cards, but it is always chosen by the Alpha Wolf when actioning.)
The Alpha Wolf chooses a non-Werewolf and replaces their role without looking with the Werewolf Center Card.
Mystic Wolf
The Mystic Wolf chooses a non-Werewolf and learns their role.
Minion
The Minion learns all the Werewolves' identities, but the Werewolves do not learn theirs. The Minion wins with the Werewolves, or, if no Werewolves exist, with the Town.
Masons
The Masons learn the identity of each other.
Seer
The Seer learns another player's role.
Apprentice Seer
The Apprentice Seer learns one of the Center Cards.
Paranormal Investigator
The Paranormal Investigator learns up to two players' roles, or until they learn a Tanner or a Werewolf. If they learn a Tanner or Werewolf, they become that role and stop their action immediately.
Robber
The Robber learns a player's role, and then swaps their role with that player.
Witch
The Witch may look at a Center Card. If they do, they can swap that card with any player's role (including their own).
Troublemaker
The Troublemaker may swap two players' roles.
Village Idiot
The Village Idiot may swap all other players' roles left or right.
Drunk
The Drunk may pick another player's role and swap it with theirs without learning either.
Insomniac
The Insomniac learns their role.
Revealer
The Revealer learns another player's role. If the role is not a Werewolf or Tanner, that role is revealed to all players.
Curator
The Curator gives a random Artifact Token to a player. The receiving player looks at the Artifact at the beginning of the round, which takes precedent over their role.
Villager
You have no action.
Tanner
You win if you die at the end of the game. If you die, the Werewolves lose. If no Werewolves are in the game and only you die, the Town and Tanner both win.
Hunter
If you are voted at the end, the player you are voting for dies as well.
Bodyguard
The player you vote for is protected from being voted. If that player has the most votes, the players with the second most votes dies instead.
Prince
You cannot be voted. If you have the most votes, the player with the second-most votes dies instead.
Dream Wolf
You do not learn the other Werewolves' identities, but they learn yours.
Claw of the Werewolf
You are now a Werewolf.
Brand of the Villager
You are now a Villager.
Cudgel of the Tanner
You are now a Tanner.
Void of Nothingness
This artifact does nothing.
... There's two dumb Artifacts that I won't include because they're dumb.
So, as a Night action focused game type, it works really well. I think it could be a fun mode to run as a small type.