We tried this today with a three-way battle between Ultramarines, my Void Legion, and my son's Tau.
The point limit was 1000. Three objectives with each player getting to place one each. The objectives must be within 24" of the center of the table.
Roll for deployment order. Place one unit anywhere you want, except within 12" of another unit. Roll for standard scatter. If your unit would go off the table it is not destroyed it just sits on the edge. If the unit scatters within 12" of another unit that is okay. If you scatter into area terrain or difficult terrain that is fine. If you scatter into impassable terrain just place the unit up next to it. Using common sense will help things work out.
Then the next player deploys one of their units following the above guidance. And so on, and so on, and s.......
It is a lot of fun and gets you right into the fight. No unit is right on top of another unless it scatters there, making for some fun tactical decisions.
For extra randomness, roll for at the beginning of every round for player turns.
In the end, the Tau manuevered and sniped the SM and Ultramarines (who were busy tearing each other up!). Tau for the win!