Just had the idea, but it works, its simple. The players that want to roll off, but not interfere the ongoing game just claim another players roll as theirs.
Example:
Red: Blues next 8-stack roll is mine
blues loses with a 26
Teal: Greens next 8-stack is mine
Green wins with 23
Red 26 - teal 23
red wins over teal, teal flags out.
Sounds more complicated than it is