Bench -> Paused bench, incline bench, close grip bench etc.
Deadlift -> Stiff-legged deads, Romanian deads, front squats and barbell rows
Squat -> Paused squats, front squats
Press -> Switching to seated pressing + dumbbell press
Choosing your assistance work boils down to what you actually need to accomplish to improve your lifts. In many cases, a secondary session of the same exact movement per week is great.