Hi Guys,
here's an experimental scenario that was inspired by the Broken Alliance scenario in the rulebook.

The game is designed for 2v2, 3v3 or even more players- The narrative can be modified, but the idea is the same:

each player starts the game as part of a 'team', but each faction within the team is only grudgingly at peace with one another. The slightest mishap can trigger rivalries that can become 'total war'.

Each player is competing to have troop-choices on scoring locations and/or making most kills by using the standard 5th ed random objectives (remember, you're also competing against your team-mates)

Special Rules:
Each turn, players roll-off to decide their turn order.

Players cannot attack team-mates.. yet (see further rules)

At the start of each turn, a player rolls D3 for 'Special Orders', the result is as follows:
1- Friendly Fire- One of your allies have attacked you, but you don't know who it was! Allocate 2D6 Strength 6 AP- hits to any of your non-vehicle units OR declare total war (only on turns 4 and above)
2-3 Command Ally- Choose an allied non-HQ unit, you can command it for the duration of this turn.

If either 'team' receives more than 3 friendly-fire incidents, 'total war' is declared for both teams.

Total War:
Players roll-off for turn order at the start of the turn.
No more than 2 opposing sides may participate in a close-combat.

Players may shoot into close-combat if it doesn't involve their own troops- for each hit, roll D6. If you roll 4+, you hit the target player's unit. If you roll 1-3, you hit the other player.

Players can attack anyone.
No more 'Special Orders' rolls will be made.

The idea is that players will try to manipulate their teammates until the last possible moment before declaring total war so that they are in the best position possible.

possible narrative-
3v3: Daemonhunters, Tau, Space Marines VS Tyranids, Chaos Daemons, Chaos Marines
an Inquisitor and his Grey Knight retinue is closely monitoring a Space Marine Captain and his dealings with a Tau hunter cadre as they plan to thwart a Chaos ritual to attract Tyranids to this sector.
The Inquisitor is prepared to execute the Marines for employing the blasphemous technology of the Tau, and the Chaos ritual to bring the Tyranids under their command can come undone at anytime.

feel free to improve!