Probably not many - Picard was the first one they knew of being assimilated and that appeared like a special case. I can't see Starfleet equipping escape pods with suicide pills either. More likely after First Contact events.
I'm not sure Klingons could have scooped up the survivors. They'd have gone straight after the cube to fight it - and would have been destroyed. So if Sisko had been picked up by them, he would be dead. It's unlikely they couldn't catch up with the cube as the Enterprise did so and made no mention of overtaking support ships.